Complex sentence: The failure of airlines to broadly accept the Convair 880 and 990 led Convair to suffer what at the time was one of the largest corporate losses in history, although they later profitably built fuselages for the DC-10, KC-10 and MD-11.
Split into simpler sentences: The failure of airlines to broadly accept the Convair 880 and 990 led Convair to suffer what at the time was one of the largest corporate losses in history. Although they later profitably built fuselages for the DC-10, KC-10 and MD-11.