GENERAL AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)

12 Months Ended

Dec. 31, 2017

Property, Plant and Equipment [Table Text Block]

Property and equipment are recorded at cost and depreciated using the straight-line method over their estimated useful lives less an estimated salvage value, which are as follows:



	Estimated Useful Life	Estimated Salvage Value
Aircraft and other flight equipment:
Boeing 737, Airbus A319/320, and E175 aircraft	20-25 years	10%
Bombardier Q400 aircraft	15 years	10%
Buildings	25 - 30 years	—%
Minor building and land improvements	10 years	—%
Capitalized leases and leasehold improvements	Generally shorter of lease term or estimated useful life	0-10%
Computer hardware and software	3-10 years	—%
Other furniture and equipment	5-10 years	—%

Liabilities from Mileage Plan [Table Text Block]

Frequent flyer program deferred revenue and liabilities included in the consolidated balance sheets (in millions):



	2017		2016
Current Liabilities:
Other accrued liabilities	$	519	$	484
Other Liabilities and Credits:
Deferred revenue	699		638
Other liabilities	26		21
Total	$	1,244	$	1,143

Revenue from Mileage Plan [Table Text Block]

Frequent flyer program revenue included in the consolidated statements of operations (in millions):



	2017		2016		2015
Passenger revenues	$	380	$	293	$	267
Other—net revenues	482		429		329
Total frequent flyer program revenues	$	862	$	722	$	596