An off-duty British pilot helped to rescue a plane after a pilot stabbed his colleague in the cockpit and tried to crash the aircraft en route to Israel, a passenger has said.

Passengers and crew subdued the alleged attacker as the FlyDubai plane dropped from 33,000 feet to 17,000 feet (10,000 metres to 5,100 metres) in about a minute.

The aircraft, travelling from the United Arab Emirates to Tel Aviv carrying dozens of passengers, was forced to make an emergency landing in Saudi Arabia.

One passenger, Almog Itali, has told media that one of the off-duty pilots onboard who stabilised the plane was British.

In a short translated clip on the BBC, Mr Itali said: “There were two pilots in the front, one stabbed the other, and there were two spare pilots who were supposed to operate the next flight.

“The relief pilots are European, one of them British, who entered (the cockpit) and pulled the aircraft up, pulled the yoke, stabilised the plane and landed us in Saudi Arabia.”

Israeli Prime Minister Benjamin Netanyahu has said Saudi Arabia has arrested the pilot of a FlyDubai flight.

Around two and a half hours after leaving Dubai, the plane sent an emergency alert, according to publicly available flight tracking information.

The flight then descended abruptly before making an erratic circle close to the Jordanian border and landing in Tabuk about an hour later, according to Flightradar24.

Passengers at Ben Gurion International Airport (Ariel Schalit/AP)

AP

Video footage circulating on social media shows two men on the floor of the plane, with bloody wounds.

Two people appear to be providing emergency medical treatment, while two others guard the cockpit.

A FlyDubai spokesperson has said: “An altercation occurred in the flight deck of flight FZ 1073, operating from Dubai International to Ben Gurion International Airport, on September 30.

“The aircraft was successfully secured by on-duty FlyDubai crew travelling on the flight, who diverted and landed the aircraft safely at Tabuk Airport. All passengers and crew are safe and accounted for.

“We have deployed two replacement aircraft to Tabuk to relieve the passengers and crew.

“This incident has no impact on other scheduled operations across the FlyDubai network.”

They added that at this stage the “underlying reasons and motives” for the attack are unknown, and are subject to a formal investigation.