Claims Bieber smoked so much pot it made flight crew high

THE American airline regulator is looking into claims that popstar Justin Bieber and his entourage smoked enough marijuana in flight to affect the plane's crew.

CNN reports the allegations centre on Bieber and his father refusing the pilot's demand for them to stop smoking pot on the flight.

Authorities said the pilots donned oxygen masks to avoid the smoke, fearing they could fail future drug tests.

Interfering with a flight crew can be a criminal offence punishable by 20 years in prison or fines up to $250,000.