Lack of Moral Fibre or LMF was a punitive designation used by the Royal Air Force during the Second World War to stigmatize aircrew who refused to fly operations.
[3][4] By the summer of 1940, senior commanders became concerned that medical officers were removing too many men from flying duty.
[10][11] A man classified in categories (i) or (ii) would lose his flying badge, "to prevent his getting a lucrative job as a pilot in civil life".
[12] Officers would lose their commissions and be refused ground jobs in the RAF, while NCOs would be reduced to aircraftman second class and assigned menial tasks, such as latrine duty, for at least three months.
[2] RAF psychiatrists, while acknowledging the deterrent effect, considered it harsh and deficient in failing to take account of individual situations.