Your claim: "crew rest requirement was the reason given, which actually means not enough crew" is incorrect. Consider: when a flight is delayed for a repair (m

Your claim: "crew rest requirement was the reason given, which actually means not enough crew" is incorrect. Consider: when a flight is delayed for a repair (maintenance delay) does that equal "not enough aircraft"? Carriers can't staff surplus crews any more than they can sit on spare aircraft, both which are small, very carefully computed quantities. It is a crew rest requirement delay.