A hero 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 said.

The FlyDubai aircraft from Dubai carrying 180 passengers was forced to make an emergency landing in Saudi Arabia on Wednesday, with Israel scrambling warplanes.

The plane plunged more than 17,000 ft in less than two minutes from its cruising altitude of 34,000ft during the incident, flight tracking data shows.

Passengers and crew on the Flydubai jet reportedly stopped the alleged attacker, with one passenger Almog Itali, telling media that a British off-duty pilot on board helped stabilise the 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.”

Israel's Prime Minister Benjamin Netanyahu said the pilot who launched the alleged attack has been arrested and is being questioned by Saudi authorities.

Mr Netanyahu said: “During the flight, as they were approaching Israel, one of the pilots stabbed the other pilot and, apparently, tried to crash the plane with its passengers on board.

“I spoke with one of the Israeli passengers. He told me that the plane went into a spin and began to descend. He told me that, somehow, he managed to break into the cockpit with one of the crew members and, together, they overpowered the pilot who had carried out the stabbing while he was attempting to sabotage the aircraft's systems.

“Another air crew who was on the plane entered the cockpit and managed to stabilise the aircraft.

“I salute these heroes who demonstrated extraordinary resourcefulness and courage. They saved many lives and prevented a major disaster.”

It was reported earlier that the flight between Dubai and Tel Aviv had to be diverted after the pilots started brawling.

An anonymous ​Israeli official is reported to have said the pilots on board the flight transmitted ​emergency signals after getting into a physical altercation with each other.

International news outlets reported that passengers were screaming during the incident, during which the plane is said to have plunged almost 20,000 feet.

One anonymous passenger told i24NEWS: “We heard screams and saw blood. There were moments when we thought we weren’t going to make it out alive.”

An airline spokesperson ​told the news agency that the flight experienced an "incident" en route to Tel Aviv and diverted to Tabuk, where it landed safely.

It was said to have been in Jordanian airspace at the time the signals from the cockpit were sent.

All passengers were safe and accounted for, added a spokesman for the Emirati government-owned airline that is based in Dubai.

The Boeing 737 plane is said to have transmitted a second general emergency signal before landing ​at Tabuk airport in north-west Saudi Arabia.

Israeli authorities said that fighter jets had been scrambled upon receipt of the second emergency signal.

Mr Netanyahu was briefed over the ⁠incident, his office confirmed.

In a statement, Mr Netanyahu’s office said earlier: “Following concerns over an aviation incident, Prime Minister Netanyahu held consultations on the matter and is monitoring developments.

“The incident is under control, and all measures are currently being deployed in order to return the Israeli passengers safely to Israel.”

Israel, currently embroiled in a conflict in Gaza and with Iran and in its proxies, has no official diplomatic relations with Saudi ​Arabia.