By Will Guisbond The aftermath of the near-catastrophic FlyDubai flight that miraculously ended with a safe landing has largely focused on the desperate fight between the two pilots and the heroic effort by passengers and a reserve crew to stabilize the plunging jetliner.

But the performance of the aircraft itself also appears to have defied the odds, given the Boeing Co. 737 Max plummeted almost vertically at one point as the two men battled for control of the cockpit. The plane eventually touched down in Saudi Arabia, despite the breakneck maneuvers that seemed to damage some parts of the aircraft, drawing online praise of Boeing’s design from US President Donald Trump.

Investigators are still working to determine the facts of the incident, but interviews with a test pilot and a review of the plane’s design features show the aircraft — and the more than 170 people on board — likely survived thanks to layers of redundancy in aviation and, perhaps, a little luck.

Preliminary information indicates that the aircraft dove, climbed rapidly and then dove again after the co-pilot attacked his colleague. Passengers who rushed to the front of the plane were able to stabilize the situation, pulling the attacker off the injured pilot and arresting the airplane’s rapid descent that had sent the rest of the cabin into chaos.

When the plane touched down in Tabuk, Saudi Arabia, unverified images circulating on social media showed a portion of the aircraft’s rudder, which controls where the nose of the jet is pointing without rolling the wings, had been torn off.

According to FlightRadar24, the aircraft at one point was descending at more than 32,000 feet per minute, a dive whose recovery would’ve likely seen passengers experience crushing gravitational forces typically stomached by fighter pilots and astronauts.

When an aircraft is certified, it is intentionally put in situations that are never expected to occur during normal operations. The Boeing 737 Max involved in the incident is the newest, more efficient iteration of the workhouse single-aisle plane first approved in the 1960s, upgraded with modern engines and avionics.

“Why do you test out there? The answer is because of the potential for inadvertent exceedances of those limits,” said Bob Stoney, a former US Federal Aviation Administration pilot who headed flight testing for several Boeing aircraft including the 737-900ER and led the Max models’ return to service after two fatal crashes last decade.

The certification process also requires that aircraft go through rigorous ground tests, including intentionally stressing wings to failure.

Federal aviation regulations mandate large commercial airliners be tested well beyond their published normal maximum operating limit speed, which for a 737 Max 8 is about 630 miles (1,000 kilometers) per hour, but can change depending on altitude and weather conditions, according to the FAA. The FlyDubai aircraft clocked a maximum speed of about 690 mph during its dive, near the speed of sound at that altitude, according to preliminary data from tracking service FlightRadar24.

Damage to any flight control surface like the rudder is typically a critical event that changes how the aircraft flies, potentially endangering all onboard.

Stoney said there is a requirement to complete tests for a jammed rudder during certification, but not for the piece to be outright missing. He explained the two cases are relatively aerodynamically similar, as pilots in both situations must fly as if they have lost the rudder entirely.

The rudder in a large jet like the 737 is particularly critical during landing, Stoney said, adding that doing so without one in high wind conditions or when the wind is not aligned with the runway is challenging. However, he said the loss of a wing or tail flap would generally be harder to recover from in any situation.

The damaged rudder may have been one of many difficult circumstances encountered by the off-duty pilots who happened to be on board the FlyDubai aircraft when the attack took place.

Israeli Prime Minister Benjamin Netanyahu said that after being stabbed, the captain managed to unlock the door to the cockpit — which can only be done from inside — to call for help. Passengers intervened, and the off-duty pilots then took control of the airplane.

“I’ve been a pilot for 17 years, I’ve been a captain for the past 11 years, I know what’s happening in a flight even with my eyes closed,” FlyDubai Captain Smit Machchhar said during a Friday call with Indian Prime Minister Narendra Modi from the hospital. “When I was on the ground, I realized that the aircraft is going down. And I told myself, ‘This is the last push, Smit. The door is right there.’”In a video released by Netanyahu’s office on social media, the passenger who claims to have been first to the cockpit said he grabbed the aircraft controls and pulled them back to arrest the rapid dive after yanking the attacker off the captain.

The passenger, identified as Yaniv Hayun, said this was an action he knew to take because he watches the popular Air Crash Investigation television series on National Geographic.

The Boeing 737 has two central steering yokes shaped like horns to maneuver the plane, unlike an Airbus SE A320, which is flown using control sticks positioned off to the side of each pilot’s seat — and which might have been less intuitive to manipulate for an amateur.

Throughout aviation history, there are examples of accidents where layers of safety and redundancy helped avert tragedy, but also plenty where seemingly miraculous circumstances were the difference between a safe outcome and a disaster.

Perhaps most famous was the 2009 accident dubbed “the miracle on the Hudson,” when a US Airways Airbus A320 landed on the Hudson River following an extremely rare dual engine failure upon ingesting a flock of birds. All 155 people on board survived.

“Consequently, this accident has been portrayed as a ‘successful’ ditching,” the US National Transportation Safety Board said in its final report at the time.

“However, the investigation revealed that the success of this ditching mostly resulted from a series of fortuitous circumstances,” namely that the pilot had nearly 20,000 flight hours, the plane was equipped with extra slides and life rafts, and the ditching took place in an area close to large boats that immediately came to the rescue, the report said.

As if to warn the industry to remain vigilant despite the positive outcome, the report added: “The investigation revealed several areas where safety improvements are needed.”