There are many reasons behind the MD-11's downfall. The main factor being the lack of range that the airplane possesed. McDonnell Douglas promised that the aircraft could do X amount of nm with X amount of cargo/pax on board when in fact with a full payload the MD-11 could do nowhere near this range. The original launch customer was American Airlines and they themselves were very disapointed with the aircrafts lack of range. There were other reasons like instability within the company itself(at this stage McDonnell Douglas were struggling to stay in the competition with Boeing- the new 777 with only 2 engines and a ranger than the MD-11, and also the Airbus A330 and A340- both of which were in fact cheaper to run and maintain than the MD-11 was.) With the A330/A340 and 777 well-established, there appeared to be no room for a third entry. Despite it's problem with range the MD-11 is apparently a "pilot's airplane" in that it requires a lot of pilot input to operate efficiently.