10 апреля: совершил полет Boeing DH-4M с американским двигателем Liberty, ставший лицензионным вариантом известного британского самолета. BOEING-DE HAVILLAND D.H.4M. In the lean years immediately after the First World War contracts for new military types were sparse and most companies had to be content with re-working wartime types - the de Havilland D.H.4 was a typical example. Some 1,538 D.H.4s were modernised by no fewer than ten different U.S. firms from 1919 to 1923. Boeing received two separate contracts successively, for fifty-three D.H.4Ms and ninety-seven D.H.4M-1s.