Complex sentence: The firm then built the Moss M.A.2 in early 1939, which differed from the earlier aircraft in having a 90 h.p Blackburn Cirrus Minor I and a covered cabin.
Split into simpler sentences: The firm then built the Moss M.A.2 in early 1939. This differed from the earlier aircraft in being powered by a 90 h.p Blackburn Cirrus Minor I and having a covered cabin.