A flydubai Boeing 737 was cruising at about 34,000 feet when it suddenly lost more than 14,000 feet in less than a minute on its way from Dubai to Tel Aviv on 30 September. Flight-tracking data showed the aircraft descending at an extraordinary rate before it recovered and eventually landed safely in Tabuk, Saudi Arabia.
A passenger jet can lose thousands of feet in seconds without necessarily falling out of the sky. What matters is how the aircraft is descending, how quickly its speed is changing and whether pilots can keep the aircraft within its operating limits. The flydubai incident offers a dramatic example of what happens when a Boeing 737 suddenly loses altitude at high speed.
So how could a passenger jet lose thousands of feet so quickly and still remain flyable?
What could have caused such a sudden descent?
A commercial aircraft does not normally lose 14,000 feet in 37 seconds. Flightradar24 data showed FZ1073 leaving its cruise altitude of about 34,000 feet and undergoing a steep descent before climbing again and eventually settling at around 14,000-15,000 feet.
The available tracking data, however, cannot tell us everything that was happening inside the cockpit.
If a pilot is attacked or becomes incapacitated while the aircraft is being controlled, the aircraft can enter an abnormal attitude. A Boeing 737 can be flown manually, through its autopilot or through a combination of automated systems and pilot inputs. If the aircraft’s nose drops and the pilots do not immediately correct it, gravity causes it to lose altitude and its speed can increase rapidly.
That could help explain why the flight lost altitude so quickly, but investigators will need cockpit voice recordings, flight-data recordings and aircraft-system information to establish exactly what happened.
The dramatic descent came amid a reported struggle in the cockpit. Israeli officials said the co-pilot stabbed captain Smit Machchhar and attempted to take control of the aircraft. Passengers and other crew members intervened. Flydubai confirmed an altercation on the flight deck, but the airline has not publicly established exactly how it began or what happened during the descent. The incident is under investigation.
Why didn’t the 737 simply fall out of the sky?
This is where the difference between a rapid descent and a free fall matters.
An aircraft remains capable of generating lift as long as air is flowing over its wings. A steep descent can therefore involve the aircraft travelling rapidly downward while still being aerodynamically controlled.
But speed becomes a major concern.
The faster an aircraft travels, the greater the aerodynamic forces acting on it. Airliners therefore have maximum operating speeds and Mach limits. Pilots managing an emergency descent must balance two competing demands: lose altitude quickly while preventing the aircraft from accelerating beyond its operating limits.
FAA guidance for emergency descents calls for pilots to reduce thrust, control the aircraft’s attitude and use speed brakes where appropriate while monitoring airspeed.
This is also why the reported tracking figure of about 598 knots should not simply be described as the aircraft travelling at 598 knots through the air. Flightradar24 was reporting groundspeed, which is different from indicated airspeed, true airspeed and Mach number. Wind conditions can make those figures substantially different.
Airspeed is the speed of an aircraft relative to the surrounding air, while ground speed is the aircraft’s speed relative to the ground.
Indicated airspeed is the raw speed read directly from the aircraft’s cockpit indicator, true airspeed is the actual physical speed moving through the surrounding air mass, and Mach number is the ratio of true airspeed to the local speed of sound.
“The flight began a steep descent, followed by a sharp ascent, followed by another sharp descent. The aircraft’s altitude oscillated around 15,000 feet and ground speed varied significantly throughout the rest of the flight,” a Flightradar24 report said.
What may have saved the aircraft?
The aircraft appears to have recovered from the initial descent rather than continuing downward.
According to flight-tracking data, the 737 first descended from around 34,000 feet, then climbed again before settling at a lower altitude. Reuters reported that passengers and crew entered the cockpit and that other flydubai pilots who were travelling on the aircraft helped regain control.
That detail is important because it suggests the aircraft remained controllable despite the chaos in the cockpit.
There was also a basic layer of protection built into the aircraft itself: the 737’s automated flight systems can maintain altitude, heading and other parameters when properly engaged, although they do not remove the need for pilots to monitor and control the aircraft.
Once control was regained, the crew could keep the aircraft at a lower altitude and divert to an airport rather than attempting to continue to Tel Aviv.
Why was the aircraft taken down to a lower altitude?
A lower altitude can be useful during an emergency for several reasons.
If there is a problem involving pressurisation, oxygen availability, flight controls or the pilots themselves, being closer to the ground gives the crew more options and reduces the time required to reach an airport.
It also gives the aircraft more opportunities to stabilise after an abnormal flight condition.
In this case, the aircraft eventually landed at Tabuk, where both pilots were taken to hospital, according to the Saudi airport authorities. Flydubai said everyone on board was safe and accounted for.
The 37 seconds tell only part of the story
The most striking number from the incident is the reported 14,000-foot loss in roughly 37 seconds. But that figure alone cannot tell us whether the aircraft was in a dive, what its exact airspeed was, which automated systems were active or what inputs were being made in the cockpit.
Those details should emerge from the investigation.
What is already clear is that the aircraft survived an extraordinary loss of altitude, regained a stable flight condition and remained controllable long enough to reach an emergency landing site.
The crucial question for investigators will be what caused FZ1073 to enter that descent in the first place, and how control was restored.