INVENTORIES

The majority of our inventories are for business-jet aircraft. Our inventories are stated at the lower of cost or net realizable value. Work in process represents largely labor, material and overhead costs associated with aircraft in the manufacturing process and is based primarily on the estimated average unit cost in a production lot. Raw materials are valued primarily on the first-in, first-out method. We record pre-owned aircraft acquired in connection with the sale of new aircraft at the lower of the trade-in value or the estimated net realizable value.

Inventories consisted of the following:



	September 30, 2018		December 31, 2017
Work in process	$	4,688	$	3,872
Raw materials	1,425		1,357
Finished goods	45		51
Pre-owned aircraft	89		23
Total inventories	$	6,247	$	5,303

The increase in total inventories during the nine-month period ended September 30, 2018, was due primarily to the ramp-up in production of the new G500 and G600 aircraft programs in our Aerospace segment. We received type certification from the U.S. Federal Aviation Administration (FAA) for the G500 aircraft in July 2018 and delivered the first G500 aircraft in the third quarter of 2018. Additionally, we continue to progress toward anticipated FAA type certification later this year and entry into service in 2019 of the new G600 aircraft.