The US Transport Security Administration is planning refresher courses for staff after a passenger was able to get on board a flight with a box cutter.

The Frontier Airlines flight from Cincinnati to Tampa had to be diverted to Atlanta late on Friday, after reports the man was threatening passengers and crew.

An investigation later revealed the man had tried to take two box cutters through security before boarding the flight but they weren’t picked up by scanning equipment.

A manual search of one of the man’s bags did find one and the blades were removed before the box cutter was handed back to the passenger.

The man was arrested once the aircraft touched down in Atlanta and a second boxcutter was found.

Box cutters have been banned in hand luggage since the 9/11 attacks.

The TSA said the agents who conducted the searches didn’t follow the correct procedures and are now undergoing ‘training status for remediation on CT image review and physical search procedures’ and more ‘refresher’ training is being planned for TSA agents nationally.

Frontier Spokeswoman Jennifer de la Cruz told the New York Times on Friday that all passengers were given overnight hotel accommodation in Atlanta and a new flight was scheduled for Tampa the following morning.