Prior results have been adjusted to reflect the adoption of a new revenue recognition accounting standard (ASC 606) in the first quarter of 2018 as well as the realignment for military derivative aircraft in the first quarter of 2019. Effective at the beginning of 2019, all revenues and costs associated with military derivative aircraft production are reported in the Defense, Space & Security segment. Revenues and costs associated with military derivative aircraft production were previously reported in the Commercial Airplanes and Defense, Space & Security segments. Business segment data for 2018 and 2017 reflects the realignment for military derivative aircraft.
Beginning in 2003, Boeing Commercial Airplanes business segment results as well as consolidated results have been presented on a program accounting basis. Previously, business segment results were presented on a unit cost basis and consolidated on a program accounting basis. The table provided above, provides both program accounting and unit cost accounting information.
* This is a non-GAAP measure. Management is providing Commercial Airplanes' Earnings from Operations computed using non-GAAP unit-cost based accounting in response to requests from specific investors. The company does not intend for unit-cost information to be considered in isolation or as a substitute for program accounting. The basic difference between unit-cost based accounting and program accounting is that unit cost accounting determines cost of sales based on a more discrete costing of the individual airplane while program accounting determines cost of sales based on the average profitability over the airplane program accounting quantity. Unit cost accounting records cost of sales based on the cost of specific units delivered, and to the extent that inventoriable costs exceed estimated revenues, a loss is not recognized until delivery is made. Note 1 of the Company's 10-K filing describes program accounting.