Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2013

Schedule of Information Related to Amounts Recorded Related to Frequent Flyer Programs

The following table provides additional information related to the frequent flyer program (in millions):

Year Ended December 31,	Cash Proceeds from Miles Sold		Other Revenue Recognized Upon Award of Miles to Third-Party Customers (a)		Increase in Frequent Flyer Deferred Revenue for Miles Awarded (b)		Increase (Decrease)  in Advanced Purchase of Miles (c)
2013	$	2,903	$	903	$	2,174	$	(174)
2012		2,852		816		2,036		—
2011		3,121		566		2,357		198
(a) This amount represents other revenue recognized during the period from the sale of miles to third parties, representing the marketing-related deliverable services component of the sale.
(b) This amount represents the increase to frequent flyer deferred revenue during the period.
(c) This amount represents the net increase (decrease) in the advance purchase of miles obligation due to cash payments for the sale of miles in excess of (less than) miles awarded to customers.

Estimated Useful Lives of Property and Equipment

The estimated useful lives of property and equipment are as follows:

	Estimated Useful Life (in years)
Aircraft and related rotable parts		25 to 30
Buildings		25 to 45
Other property and equipment		4 to 15
Computer software		5
Building improvements		1 to 40