TransDigm's sales are concentrated in the aerospace industry. The Company’s customers include: distributors of aerospace components, commercial airlines, large commercial transport and regional and business aircraft OEMs, various armed forces of the United States and friendly foreign governments, defense OEMs, system suppliers, and various other industrial customers.

The majority of the Company's revenue is recorded at a point in time. Revenue is recognized from the sale of products when control transfers to the customer, which is demonstrated by our right to payment, a transfer of title, a transfer of the risk and rewards of ownership, or the customer acceptance, but most frequently upon shipment where the customer obtains physical possession of the goods.

In some contracts, the Company found that control transferred to the customer over time, primarily in contracts where the customer is required to pay for the cost of both the finished and unfinished goods at the time of cancellation plus a reasonable profit relative to the work performed for products that were customized for the customer. Therefore, we recognize revenue over time for those agreements that have a right to margin and where the products being produced have no alternative use.

Based on our production cycle, it is generally expected that goods related to the revenue will be shipped and billed within the current year. For revenue recognized over time, we estimate the amount of revenue attributable to a contract earned at a given point during the production cycle based on certain costs, such as materials and labor incurred to date, plus the expected profit, which is a cost-to-cost input method.

The Company’s payment terms vary by the type and location of the customer and the products or services offered. The Company does not offer any payment terms that would meet the requirements for consideration as a significant financing component.

Shipping and handling fees and costs incurred in connection with products sold are recorded in cost of sales in the condensed consolidated statements of income, and are not considered a performance obligation to our customers.

The Company pays sales commissions that relate to contracts for products or services that are satisfied at a point in time or over a period of one year or less and are expensed as incurred. These costs are reported as a component of selling and administrative expenses in the unaudited condensed consolidated statements of income.

Contract Assets and Liabilities - Contract assets reflect revenue recognized and performance obligations satisfied in advance of customer billing or reimbursable costs related to a specific contract. Contract liabilities relate to payments received in advance of the satisfaction of performance under the contract. We receive payments from customers based on the terms established in our contracts. The following table summarizes our contract assets and liabilities balances (in millions):



	December 28, 2019		September 30, 2019		Change
Contract assets, current ⁽¹⁾	$	43	$	44	$	(1	)
Contract assets, non-current ⁽²⁾	6		7		(1		)
Total contract assets	49		51		(2		)
Contract liabilities, current ⁽³⁾	18		18		—
Contract liabilities, non-current ⁽⁴⁾	16		13		3
Total contract liabilities	34		31		3
Net contract assets	$	15	$	20	$	(5	)

For the thirteen week period ended December 28, 2019, the revenue recognized that was previously included in contract liabilities was not material.