PROPERTY AND EQUIPMENT

The Company's property and equipment consists primarily of cargo aircraft, aircraft engines and other flight equipment. Property and equipment, to be held and used, is summarized as follows (in thousands):



	December 31, 2017			December 31, 2016
Flight equipment	$	1,801,808		$	1,541,872
Ground equipment	53,523			49,229
Leasehold improvements, facilities and office equipment	26,897			27,364
Aircraft modifications and projects in progress	121,760			113,518
	2,003,988			1,731,983
Accumulated depreciation	(844,026		)	(730,991		)
Property and equipment, net	$	1,159,962		$	1,000,992

CAM owned aircraft with a carrying value of $697.4 million and $524.3 million that were under leases to external customers as of December 31, 2017 and 2016, respectively. Minimum future payments from external customers for leased aircraft and equipment as of December 31, 2017 is scheduled to be $146.6 million, $111.0 million, $95.1 million, $76.6 million and $63.0 million for each of the next five years ending December 31, 2022.

The Company’s accounting policy for major airframe and engine maintenance varies by subsidiary and aircraft type. The costs of airframe maintenance for Boeing 767-200 operated by ABX are expensed as they are incurred. The costs of major airframe maintenance for the Company's other aircraft are capitalized and amortized over the useful life of the overhaul. Many of the Company's General Electric CF6 engines that power the Boeing 767-200 aircraft are maintained under “power by the hour” and "power by the cycle" agreements with an engine maintenance provider. Further, in May 2017, the Company entered into similar maintenance agreements for certain General Electric CF6 engines that power many of the Company's Boeing 767-300 aircraft. Under these agreements, the engines are maintained by the service provider for a fixed fee per cycle and/or flight hour. As a result, the cost of maintenance for these engines is generally expensed as flights occur. During their term, these maintenance agreements contain provisions for a minimum level of flight activity. Maintenance for the airlines’ other aircraft engines, including those powering Boeing 757 aircraft, are typically contracted to service providers on a time and material basis and the costs of those engine overhauls are capitalized and amortized over the useful life of the overhaul.