Spirit Airlines, Inc. ("Spirit" or the "Company") headquartered in Miramar, Florida, is an ultra low-cost, low-fare airline that provides affordable travel opportunities principally throughout the domestic United States, the Caribbean and Latin America. The Company manages operations on a system-wide basis due to the interdependence of its route structure in the various markets served. As only one service is offered (i.e., air transportation), management has concluded there is only one reportable segment.

Certain prior period amounts have been reclassified to conform to the current year's presentation. In addition, certain prior period amounts have been adjusted to reflect the adoption of Accounting Standards Update ("ASU") No. 2014-09, ("ASU 2014-09") "Revenue from Contracts with Customers," completed January 1, 2018.

The preparation of financial statements in accordance with generally accepted accounting principles in the United States of America requires the Company's management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. The Company's estimates and assumptions are based on historical experience and changes in the business environment. However, actual results may differ from estimates under different conditions, sometimes materially. Critical accounting policies and estimates are defined as those that both (i) are most important to the portrayal of the Company's financial condition and results and (ii) require management's most subjective judgments. The Company's most critical accounting policies and estimates are described below.

The Company considers all highly liquid investments with maturities of less than three months at the date of acquisition to be cash equivalents. Investments included in this category primarily consist of cash and money market funds. Cash and cash equivalents are stated at cost, which approximates fair value.

The Company's short-term investment securities are classified as available-for-sale and consist of U.S. Treasury and U.S. government agency securities with contractual maturities of twelve months or less. These securities are stated at fair value within current assets on the Company's balance sheet. For all short-term investments, at each reset period or upon reinvestment, the Company accounts for the transaction as proceeds from the maturity of short-term investment securities for the security relinquished, and purchase of short-term investment securities for the security purchased, in the Company's statements of cash flows. Realized gains and losses on sales of investments, if any, are reflected in non-operating income (expense) in the statements of operations. Unrealized gains and losses on investment securities are reflected as a component of accumulated other comprehensive income.

Accounts receivable primarily consist of amounts due from credit card processors associated with the sales of tickets and amounts due from the Internal Revenue Service related to federal excise fuel tax. The Company records an allowance for doubtful accounts for amounts not expected to be collected. The Company estimates the allowance based on historical write-offs as well as aging trends. The allowance for doubtful accounts was immaterial as of December 31, 2018 and 2017.

Property and equipment is stated at cost, less accumulated depreciation and amortization. Depreciation of operating property and equipment is computed using the straight-line method applied to each unit of property. Residual values for new aircraft, new engines, major spare rotable parts, avionics and assemblies are generally estimated to be 10%. Property under capital leases and related obligations are initially recorded at an amount equal to the present value of future minimum lease payments computed using the Company's incremental borrowing rate or, when known, the interest rate implicit in the lease.



	Estimated Useful Life
Aircraft, engines and flight simulators	25 years
Spare rotables and flight assemblies	7 to 15 years
Other equipment and vehicles	5 to 7 years
Internal use software	3 to 10 years
Capital leases	Lease term
Leasehold improvements	Lesser of lease term or estimated useful life of the improvement
Buildings	Lesser of lease term or 30 years

As of December 31, 2018, the Company had 82 aircraft, 8 spare engines and 1 flight simulator capitalized within flight equipment with depreciable lives of 25 years. As of December 31, 2018, the Company had 46 aircraft financed through operating leases with lease terms from 8 to 18 years and 12 spare engines financed through operating leases with lease terms from 2 to 14 years.

The Company capitalizes certain internal and external costs associated with the acquisition and development of internal-use software for new products, and enhancements to existing products, that have reached the application development stage and meet recoverability tests. Capitalized costs include external direct costs of materials and services utilized in developing or obtaining internal-use software, and labor cost for employees who are directly associated with, and devote time, to internal-use software projects. Capitalized computer software, included as a component of ground and other equipment in the accompanying balance sheets, net of amortization, was $13.7 million and $7.7 million at December 31, 2018 and 2017, respectively.

The Company records amortization of capitalized software on a straight-line basis within depreciation and amortization expense in the accompanying statements of operations. The Company placed in service internal-use software of $12.0 million, $1.4 million and $4.1 million, during the years ended 2018, 2017 and 2016, respectively.

The Company is required to make pre-delivery deposit payments ("PDPs") towards the purchase price of each new aircraft and engine prior to the scheduled delivery date. These deposits are initially classified as pre-delivery deposits on flight equipment on the Company's balance sheets until the aircraft or engine is delivered, at which time the related PDPs are deducted from the final purchase price of the aircraft or engine and are reclassified to flight equipment on the Company's balance sheets.

In addition, the Company capitalizes the interest that is attributable to the outstanding PDP balances as a percentage of the related debt on which interest is incurred. Capitalized interest represents interest cost incurred during the acquisition period of a long-term asset, and is the amount which theoretically could have been avoided had the Company not paid PDPs for the related aircraft or engines.

Related interest is capitalized and included within pre-delivery deposits on flight equipment through the acquisition period until delivery is taken of the aircraft or engine and the asset is ready for service. Once the aircraft or engine is delivered, the capitalized interest is also reclassified into flight equipment on the Company's balance sheets along with the related PDPs as

The Company records impairment charges on long-lived assets used in operations when events and circumstances indicate that the assets may be impaired, the undiscounted cash flows estimated to be generated by those assets are less than the carrying amount of those assets, and the net book value of the assets exceeds their estimated fair value. In making these determinations, the Company uses certain assumptions, including, but not limited to: (i) estimated fair value of the assets; and (ii) estimated, undiscounted future cash flows expected to be generated by these assets, which are based on additional assumptions such as asset utilization, length of service the asset will be used in the Company’s operations, and estimated salvage values.

Fare revenues. Tickets sold are initially deferred within air traffic liability on the Company's balance sheet. Passenger fare revenues are recognized at time of departure when transportation is provided. All tickets sold by the Company are nonrefundable. An unused ticket expires at the date of scheduled travel and is recognized as revenue at the date of scheduled travel. As of December 31, 2018 and 2017, the Company had air traffic liability ("ATL") balances of $292.0 million and $263.7 million, respectively. As of December 31, 2018, all of the ATL balance as of December 31, 2017 has been recognized.

The Company adopted ASU 2014-09 on January 1, 2018 utilizing the full retrospective method of adoption. Passenger revenues reported prior to the adoption of ASU 2014-09 are now reported as fare revenues within passenger revenues in the Company's disaggregated revenue table within Note 4, Revenue Disaggregation. Refer to Note 3, Revenue Recognition and 4, Revenue Disaggregation for information regarding the Company's adoption of ASU 2014-09.

Non-fare revenues. The adoption of ASU 2014-09 impacted the classification of certain ancillary items such as bags, seats and other travel-related fees, since they are deemed part of the single performance obligation of providing passenger transportation. These ancillary items are now recognized in non-fare revenues within passenger revenues, at the time of departure, in the Company's disaggregated revenue table within Note 4, Revenue Disaggregation.



		Year Ended December 31,
Non-fare revenue	Recognition method	2018		2017		2016
		(in thousands)
Baggage	Time of departure	$	620,154	$	488,434	$	434,269
Passenger usage fee	Time of departure	531,459		411,742		358,920
Advance seat selection	Time of departure	180,012		131,821		110,966
Other		224,283		177,495		155,539
Non-fare revenue		$	1,555,908	$	1,209,492	$	1,059,694

Changes and cancellations. Customers may elect to change or cancel their itinerary prior to the date of departure. For changes, a service charge is recognized at time of departure of newly scheduled travel and is deducted from the face value of the original purchase price of the ticket, and the original ticket becomes invalid. For cancellations, a service charge is assessed and the amount remaining after deducting the service charge is called a credit shell which generally expires 60 days from the date the credit shell is created and which can be used towards the purchase of a new ticket and the Company’s other service offerings. Both the service charge and credit shell amounts are recorded as deferred revenue and amounts expected to expire unused are estimated based on historical experience. Estimating the amount of credits that will go unused involves some level of subjectivity and judgment. However, given the relatively short period of time to expiration, this does not have a significant impact on the Company's financial statements.

The Company's frequent flyer program generates customer loyalty by rewarding customers with mileage credits to travel on Spirit. When traveling, customers earn redeemable mileage credits for each mile flown on Spirit. Customers can also earn mileage credits through participating companies such as the co-branded Spirit credit card. Mileage credits are redeemable by customers in future periods for air travel on Spirit.

The adoption of ASU 2014-09 eliminated the incremental cost method for frequent flyer program accounting, which required the Company to re-value and record a liability associated with customer flight miles earned with travel as part of the Company’s frequent flyer program with a relative fair value. Upon adoption of ASU 2014-09 on January 1, 2018, the Company recorded an increase to its air traffic liability of $12.4 million.

Passenger ticket sales earning mileage credits. Passenger ticket sales earning mileage credits provide customers with (1) mileage credits earned and (2) air transportation. The Company values each performance obligation on a standalone basis. To value the mileage credits earned, the Company considers the quantitative value a passenger receives by redeeming miles for a ticket rather than paying cash, which is referred to as equivalent ticket value ("ETV").

The Company defers revenue for the mileage credits when earned and recognizes loyalty travel awards in passenger revenue as the miles are redeemed and services are provided. The Company records the air transportation portion of the passenger ticket sales in air traffic liability and recognizes passenger revenue when transportation is provided or if the ticket goes unused, at the date of scheduled travel.

Sale of mileage credits. Customers may earn mileage credits based on their spending with the Company's co-branded credit card company with which the Company has an agreement to sell mileage credits. The contract to sell mileage credits under this agreement has multiple performance obligations, as discussed below.

The Company's co-brand credit card agreement provides for joint marketing where cardholders earn mileage credits for making purchases using co-branded cards. During 2015, the Company extended its agreement with the administrator of the FREE SPIRIT affinity credit card program to extend through 2022. The Company accounts for this agreement consistently with the accounting method that allocates the consideration received to the individual products and services delivered. The value is allocated based on the relative selling prices of those products and services, which generally consists of (i) travel miles to be awarded, (ii) licensing of brand and access to member lists and (iii) advertising and marketing efforts. The Company determined the best estimate of the selling prices by considering discounted cash flow analysis using multiple inputs and assumptions, including: (1) the expected number of miles awarded and number of miles redeemed, (2) ETV for the award travel obligation, (3) licensing of brand and access to member lists and (4) advertising and marketing efforts.

The Company defers the amount for award travel obligation as part of loyalty deferred revenue within air traffic liability on the balance sheet and recognizes loyalty travel awards in passenger revenue as the mileage credits are used for travel. Revenue allocated to the remaining performance obligations, primarily marketing components, is recorded in other revenue over time as miles are delivered. Total unrecognized revenue from future FREE SPIRIT award redemptions and the sale of mileage credits was $27.4 million and $26.6 million at December 31, 2018 and 2017, respectively. The current portion of this balance is recorded within air traffic liability and the long-term portion of this balance is recorded within deferred gains and other long-term liabilities in the accompanying balance sheets.

Mileage breakage. For mileage credits that the Company estimates are not likely to be redeemed ("breakage"), the Company recognizes the associated value proportionally during the period in which the remaining mileage credits are redeemed. Management uses statistical models to estimate breakage based on historical redemption patterns. A change in assumptions as to the period over which mileage credits are expected to be redeemed, the actual redemption activity for mileage credits or the estimated fair value of mileage credits expected to be redeemed could have an impact on revenues in the year in which the change occurs and in future years.

Current activity of frequent flyer program. Mileage credits are combined in one homogeneous pool and are not separately identifiable. As such, revenue is comprised of miles that were part of the frequent flyer deferred revenue balance at the beginning of the period as well as miles that were issued during the period.

The Company accounts for heavy maintenance and major overhaul under the deferral method whereby the cost of heavy maintenance and major overhaul is deferred and amortized until the earlier of the end of the useful life of the related asset, the end of the remaining lease term or the next scheduled heavy maintenance event.

Amortization of heavy maintenance and major overhaul costs charged to depreciation and amortization expense was $41.3 million, $53.9 million and $43.8 million for the years ended 2018, 2017 and 2016, respectively. During the years ended 2018, 2017 and 2016, the Company deferred $190.5 million, $78.2 million and $35.4 million, respectively, of costs for heavy maintenance. At December 31, 2018 and 2017, the Company had deferred heavy maintenance balance of $366.3 million and $260.5 million, and accumulated heavy maintenance amortization of $117.3 million and $160.7 million, respectively.

The Company outsources certain routine, non-heavy maintenance functions under contracts that require payment on a utilization basis, such as flight hours. Costs incurred for maintenance and repair under flight hour maintenance contracts, where labor and materials price risks have been transferred to the service provider, are expensed based on contractual payment terms. All other costs for routine maintenance of the airframes and engines are charged to expense as performed.

The Company's aircraft lease agreements often contain provisions that require the Company to return aircraft airframes, engines and other aircraft components to the lessor in a certain condition or pay an amount to the lessor based on the airframe and engine's actual return condition. Lease return costs include all costs that would be incurred at the return of the aircraft, including costs incurred to repair the airframe and engines to the required condition as stipulated by the lease. Lease return costs could include, but are not limited to redelivery cost, redelivery crew cost, fuel, final inspections, reconfiguration of the cabin, repairs to the airframe, painting, overhaul of engines, replacement of components and checks. Lease return costs are recognized beginning when it is probable that such costs will be incurred and they can be estimated. When costs become both probable and estimable, they are accrued on a straight-line basis as contingent rent, a component of supplemental rent, through the remaining lease term.

When determining probability and estimated cost, there are various other factors which need to be considered such as the contractual terms of the lease agreement, current condition of the aircraft, the age of the aircraft at lease expiration, number of hours run on the engines, number of cycles run on the airframe, projected number of hours run on the engine at the time of return, number of projected cycles run on the airframe at the time of return, the extent of repairs needed if any at return, return locations, current configuration of the aircraft, current paint of the aircraft, estimated escalation of cost of repairs and materials at the time of return, current flight hour agreement rates and future flight hour agreement rates. In addition, typically near the

lease return date, the lessors may allow reserves to be applied as return condition consideration or pass on certain return provisions if they do not align with their current plans to remarket the aircraft. As a result of the different factors listed above, management assesses the need to accrue lease return costs periodically throughout the year or whenever facts and circumstances warrant an assessment. Lease return costs will generally be estimable closer to the end of the lease term but may be estimable earlier in the lease term depending on the contractual terms of the lease agreement and the timing of maintenance events for a particular aircraft.

Some of the Company's aircraft and engine master lease agreements provide that the Company pay maintenance reserves to aircraft lessors to be held as collateral in advance of the Company's required performance of major maintenance activities. A majority of these maintenance reserve payments are calculated based on a utilization measure, such as flight hours or cycles, while some maintenance reserve payments are fixed, time-based contractual amounts. These lease agreements generally provide that maintenance reserves are reimbursable to the Company upon completion of the maintenance event. Some of the master lease agreements do not require that the Company pay maintenance reserves so long as the Company's cash balance does not fall below a certain level. As of December 31, 2018, the Company is in full compliance with such requirements and does not anticipate having to pay reserves related to these master leases in the future.

Maintenance reserve payments are reflected as aircraft maintenance deposits in the accompanying balance sheets. The Company makes certain assumptions to determine the recoverability of maintenance deposits. These assumptions are based on various factors such as the estimated time between the maintenance events, the date the aircraft is due to be returned to the lessor, the cost of future maintenance events and the utilization of the aircraft is estimated before it is returned to the lessor. When it is not probable the Company will recover amounts currently on deposit with a lessor, such amounts are expensed as supplemental rent.

The Company accounts for derivative financial instruments at fair value and recognizes them in the balance sheet in prepaid expenses and other current assets or other current liabilities. For derivatives designated as cash flow hedges, changes in fair value of the derivative are generally reported in other comprehensive income and are subsequently reclassified into earnings when the hedged item affects earnings. During 2015, the Company settled six forward interest rate swaps having a total notional amount of $120 million. These interest rate swaps fixed the benchmark interest rate component of interest payments on the debt related to three Airbus A321 aircraft, which the Company took delivery of during the third quarter of 2015. These instruments limited the Company's exposure to changes in the benchmark interest rate in the period from the trade date through the date of maturity. The interest rate swaps were designated as cash flow hedges. The Company accounts for interest rate swaps at fair value and recognizes them in the balance sheet in prepaid expenses and other current assets or other current liabilities with changes in fair value recorded within accumulated other comprehensive income (AOCI). Realized gains and losses from cash flow hedges are recorded in the statements of cash flows as a component of cash flows from operating activities. Subsequent to the issuance of each debt instrument, amounts remaining in AOCI are amortized over the life of the fixed-rate debt instrument.

The Company accounts for income taxes using the asset and liability method. The Company records a valuation allowance to reduce the deferred tax assets reported if, based on the weight of the evidence, it is more likely than not that some portion or all of the deferred tax assets will be not realized. As of December 31, 2018 and 2017, the Company recorded a valuation allowance of $0.3 million and $0.5 million, respectively. For additional information, refer to Note 17, Income Taxes.

The Company recognizes cost of employee services received in exchange for awards of equity instruments based on the fair value of each instrument at the date of grant. For the majority of awards, compensation expense is recognized on a straight-line basis over the period during which an employee is required to provide service in exchange for an award. Certain awards have performance conditions that must be achieved prior to vesting and are expensed based on the expected achievement at each reporting period. The Company has issued and outstanding restricted stock awards, stock option awards and performance share awards. Restricted stock awards are valued at the fair value of the shares on the date of grant. The fair value of share option awards is estimated on the date of grant using the Black-Scholes valuation model. The fair value of performance share awards is estimated through the use of a Monte Carlo simulation model. For additional information, refer to Note 11, Stock-Based Compensation.

The Company’s business may be adversely affected by increases in the price of aircraft fuel, the volatility of the price of aircraft fuel, or both. Aircraft fuel, one of the Company’s largest expenditures, represented approximately 32%, 27% and 24% of total operating expenses in 2018, 2017 and 2016, respectively.

The Company’s operations are largely concentrated in the southeast United States with Fort Lauderdale being the highest volume fueling point in the system. Gulf Coast Jet indexed fuel is the basis for a substantial majority of the Company’s fuel consumption. Any disruption to the oil production or refinery capacity in the Gulf Coast, as a result of weather or any other disaster, or disruptions in supply of jet fuel, dramatic escalations in the costs of jet fuel and/or the failure of fuel providers to perform under fuel arrangements for other reasons could have a material adverse effect on the Company’s financial condition and results of operations.