Loss of FE?
Back about 1979, when McDouglas had promised the unions no new two-crew plane after the DC-9, and they were following with the DC9-80, it was noticed the airliner with the best safety record of all was the 2-crew 737, followed by the DC-9.
That quashed the argument, the name was changed to MD-80, and some 3-crew 767 were run back into the factory to take out the FE position.
GB