Not cowardice - although interpreted by many as such. It was an unpleasant term for: Shell shock and Imminent mental collapse, for what ever reason.
If a member of flight crew 'went LMF' it meant that the doctor said that he might crack up during an operation. They left the station within 24 hours and the RAF soon after, It was miserable for all.
As my father said (after 4.5 years and 106 operations on night fighters) "We were more scared of going to the CO to report as LMF, than of going on the next Op. So we went on the next Op!!"
I think that the use of the term here and in regard to the DHL pilots is wrong and wildly inappropriate. Perhaps the poster can tell us why he is so judgemental about people he does not know, who are in a situation he (probably) does not know from his base in 'nyc'?