Fixed Assets

As of December 31, 2017 and 2016, fixed assets consisted of the following:



	As of December 31,
	2017			2016
	(dollars in thousands)
Telephone and computer equipment	$	3,465		$	2,787
Computer software	2,914			2,167
Furniture and fixtures	1,423			1,204
Leasehold improvements	36,702			35,092
Assets acquired under capital leases—equipment	6,920			4,075
Aircraft and related equipment	17,369			20,893
Other	58			57
	68,851			66,275
Less: Accumulated depreciation and amortization	(28,355		)	(23,867		)
	$	40,496		$	42,408

Depreciation and amortization expense related to fixed assets was $7.0 million, $7.7 million and $6.8 million for the years ended December 31, 2017, 2016, and 2015, respectively and are included in depreciation and amortization expense in the accompanying consolidated statements of operations.

On April 22, 2016, the Company entered into a transaction whereby the Company acquired a portfolio of four specialized aircraft which were on lease (See Note 2). During the year ended December 31, 2016, the Company purchased two aircraft and entered into two additional lease agreements. As of December 31, 2017 and 2016, aircraft and related equipment of $17.4 million and $20.9 million, respectively, is held for leasing purposes. One of the planes were sold during the third quarter of 2017 for a gain of $2.3 million. Depreciation expense related to leased assets was $1.5 million and $1.7 million for the year ended December 31, 2017 and 2016, respectively. As of December 31, 2017 and 2016, the accumulated depreciation related to leased assets was $1.8 million and $1.7 million, respectively.

Assets acquired under capital leases were $6.9 million and $4.1 million as of December 31, 2017 and 2016, respectively. If the assets acquired under capital leases transfer title at the end of the lease term or contain a bargain purchase option, the assets are amortized over their estimated useful lives; otherwise, the assets are amortized over the respective lease term. The depreciation of assets capitalized under capital leases is included in depreciation and amortization expenses and was $1.0 million, $1.2 million, and $1.5 million for the years ended December 31, 2017, 2016, and 2015, respectively. As of December 31, 2017 and 2016, accumulated depreciation related to assets acquired under capital leases was $3.4 million and $2.4 million respectively.