The MD-11 has a longer fuselage and bigger wings than a DC-10. Also different more modern fuel efficent engines. The cockpit is now a two seater, the Flight Engineers position being ripped out and replaced with computers. The MD-11 is much trickier to fly than the DC-10 supposively from the longer fuselage. Boeing/McDonnell Douglas have modified the software a few times to try and improve it. The MD-10 is an old DC-10 thats had its cockpit gutted and replaced with a modern computerized one thats identical to the MD-11 with no FE. So far only Cargo operators have gone with it but it is available for passenger planes (at great expense)!