A crewman broke his leg and passengers were thrown around in their seats during a mid-air emergency in a plane over the Irish Sea.
The Birmingham to Belfast Flybe flight, carrying 36 passengers and five crew, landed safely but an inquiry was immediately ordered into the incident.
It is understood three injured crew were taken to hospital - a man with a broken leg - while two women were treated for a sprained ankle and a head injury.
A passenger who suffered a minor head injury did not need hospital treatment.
A spokeswoman for the airline said the plane had experienced an "incident, the cause of which has not yet been verified."
A full emergency was declared at Belfast City Airport when the pilot radioed ahead to tell air traffic control he had a problem 10 minutes before the aircraft landed at 1.40 p.m.
Businessman Mr Alan Lowry, who was on-board, said passengers were terrified as the plane entered a sudden nosedive.
"We were up on the plane around about 20-25 minutes and we hit very bad turbulence. The plane then went into a nosedive for maybe just a few seconds and then obviously the pilot was able to take control of the plane again and put it down eventually," he added.
Belfast City Airport Marketing Manager Mr Brian Carlin said a full emergency was called after the pilot radioed ahead 40 miles from Belfast to say he had a problem on board.
However, it was called off when the pilot performed a text book landing at around 1.40 p.m., five minutes ahead of its scheduled time of arrival, he added.
PA