Coming into understanding that thanks DoT and its European counterpart, airlines in US/EU can't pull the thing which is quite common occurrence for budget airlines in SEA region.

Example: JetStar canceled flight because... it was not enough tickets (less than 3/4 of seats) sold and gave $20 vouchers to pax, even if they paid more. On all questions passengers were told to get lost and deal with their travel insurance.

Taking above into consideration, what was the most ridiculous reason for flight cancellation you've personally encountered?