Nothing sneaky aldente, just the size of the overhead lockers
But FlyBe's limit is 55cm long vs others of 56cm. Surely an extra 1 cm in length doesn't mean a bag won't fit in an overhead locker?! It's the width that matters for a Q400 and that's why FlyBe's limit is only 40 cm compare to 45 cm allowed by others.
An extra 1 cm makes no difference to stowing the cabin baggage but it does conveniently allow FlyBe to levy an extra £13.99 per sector which affects my decision making process if I have a choice!