The lever for the landing gear and the lever for the flaps were easily confused. After landing the pilots intended to retract flaps but accidentally retracted the landing gear instead.

At first they assumed their recruitment process accidentally favoured stupid people so they made sure to only recruit smart pilots. But it kept happening. Then they put a little flap on the end of the flap lever and a small wheel on the end of the gear lever and the problem went away.

I simplify. Read the full story. It is cool!