Note 8.Stock-based Compensation

On May 7, 2014, the stockholders of the Company approved the Air Lease Corporation 2014 Equity Incentive Plan (the “2014 Plan”). Upon approval of the 2014 Plan, no new awards may be granted under the Amended and Restated 2010 Equity Incentive Plan (the “2010 Plan”). As of June 30, 2018, the number of stock options (“Stock Options”) and restricted stock units (“RSUs”) remaining under the 2014 Plan is approximately 5,608,176, which includes 608,176 shares which were previously reserved for issuance under the 2010 Plan. Stock Options are generally granted for a term of 10 years and generally vest over a three year period. The Company has issued RSUs with four different vesting criteria: those RSUs that vest based on the attainment of book value goals, those RSUs that vest based on the attainment of Total Shareholder Return (“TSR”) goals, time based RSUs that vest ratably over a time period of three years and RSUs that cliff-vest at the end of a one or two year period. The Company has two types of book value RSUs — those that vest ratably over three years if the performance condition has been met, and those that vest at the end of a three-year period if the performance condition has been met. For the book value RSUs that vest at the end of the three-year period, the number of shares that will ultimately vest will range from 0% to 200% of the RSUs initially granted depending on the percentage change in the Company's book value per share at the end of the vesting period. At each reporting period, the Company reassesses the probability of the performance condition being achieved and expense is recognized based upon management’s assessment. Book value RSUs for which the performance metric has not been met are forfeited. The TSR RSUs vest at the end of a three-year period. The number of TSR RSUs that will ultimately vest is based upon the percentile ranking of the Company’s TSR among a peer group. The number of shares that will ultimately vest will range from 0% to 200% of the RSUs initially granted depending on the extent to which the TSR metric is achieved.

The Company recorded $4.9 million and $5.3 million of stock-based compensation expense related to RSUs for the three months ended June 30, 2018 and 2017, respectively. The Company recorded $8.3 million and $9.1 million of stock-based compensation expense related to RSUs for the six months ended June 30, 2018 and 2017, respectively.

Stock Options

A summary of stock option activity for the six month period ended June 30, 2018 follows:


				Remaining	Aggregate
		Exercise		Contractual Term	Intrinsic Value
	Shares	Price		(in years)	(in thousands)(1)
Balance at December 31, 2017	2,858,158	$	20.37	2.49	$	79,230
Granted	—	$	—	—	$	—
Exercised	(206,363)	$	20.00	—	$	4,903
Forfeited/canceled	—	$	—	—	$	—
Balance at June 30, 2018	2,651,795	$	20.40	1.99	$	57,204
Vested and exercisable as of June 30, 2018	2,651,795	$	20.40	1.99	$	57,204

(1)

The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying awards and the closing stock price of our Class A common stock as of the respective date.

As of June 30, 2018, all of the Company’s outstanding employee stock options had fully vested and there were no unrecognized compensation costs related to outstanding stock options as of June 30, 2018. As a result, there was no stock-based compensation expense related to Stock Options for the three and six months ended June 30, 2018 and 2017.

The following table summarizes additional information regarding exercisable and vested stock options at June 30, 2018:


	Stock Options Exercisable
	and Vested
		Weighted-
		Average
	Number of	Remaining Life
Range of exercise prices	Shares	(in years)
$20.00	2,531,795	1.95
$28.80	120,000	2.82
$20.00 - $28.80	2,651,795	1.99

Restricted Stock Units

Compensation cost for stock awards is measured at the grant date based on fair value and recognized over the vesting period. The fair value of time based and book value RSUs is determined based on the closing market price of the Company’s Class A common stock on the date of grant, while the fair value of TSR RSUs is determined at the grant date using a Monte Carlo simulation model. Included in the Monte Carlo simulation model were certain assumptions regarding a number of highly complex and subjective variables, such as expected volatility, risk-free interest rate and expected dividends. To appropriately value the award, the risk-free interest rate is estimated for the time period from the valuation date until the vesting date and the historical volatilities were estimated based on a historical timeframe equal to the time from the valuation date until the end date of the performance period.

During the six months ended June 30, 2018, the Company granted 379,480 RSUs of which 90,761 are TSR RSUs. The following table summarizes the activities for our unvested RSUs for the six months ended June 30, 2018:


	Unvested Restricted Stock Units
		Weighted-Average
		Grant-Date
	Number of Shares	Fair Value
Unvested at December 31, 2017	1,163,700	$	40.24
Granted	379,480	$	47.26
Vested	(401,959)	$	42.48
Forfeited/canceled	(35,089)	$	47.83
Unvested at June 30, 2018	1,106,132	$	41.60
Expected to vest after June 30, 2018	1,142,464	$	41.64

As of June 30, 2018, there was $27.2 million of unrecognized compensation cost related to unvested stock-based payments granted to employees. Total unrecognized compensation cost will be recognized over a weighted-average remaining period of 2.01 years.