Intangible Assets

12 Months Ended

Dec. 31, 2015

Goodwill and Intangible Assets Disclosure [Abstract]

Intangible Assets

INTANGIBLE ASSETS

Indefinite-Lived Intangible Assets

	Carrying Value at December 31,
(in millions)	2015		2014
International routes and slots	$	2,563	$	2,287
Delta tradename	850		850
SkyTeam-related assets	661		661
Domestic slots	622		622
Total	$	4,696	$	4,420

International Routes and Slots. Our international routes and slots primarily relate to Pacific route authorities and slots at Tokyo-Narita and London-Heathrow airports. During the December 2015 quarter, we acquired six London-Heathrow slot pairs for $276 million we previously leased from Air France-KLM.

Domestic Slots. Our domestic slots relate to our slots at New York-LaGuardia and Washington-Reagan National airports.

Changes to our operations could result in an impairment charge or a change from indefinite-lived to definite-lived in the period in which the changes occur or are projected to occur.

Definite-Lived Intangible Assets

	December 31, 2015					December 31, 2014
(in millions)	Gross Carrying Value		Accumulated Amortization			Gross Carrying Value		Accumulated Amortization
Marketing agreements	$	730	$	(658	)	$	730	$	(648	)
Contracts	193		(100		)	193		(92		)
Other	53		(53		)	53		(53		)
Total	$	976	$	(811	)	$	976	$	(793	)

Amortization expense was $18 million, $55 million and $70 million for the years ended December 31, 2015, 2014 and 2013, respectively. We estimate that we will incur approximately $17 million of amortization expense annually through 2020.