The Boeing 727 belly-flops hard onto the sandy floor of the Mexican desert. Its nose is torn off as its landing gear crumples like a lame horse. Inside, unbelted occupants are tossed like rag dolls, and overhead bins spew luggage and electrical wiring into the cabin.

This is a real jetliner crash, but not a catastrophe. It's an intentional crash for the new Discovery Channel program Curiosity, which airs Sunday at 9 p.m. ET. In this case, university scientists and international investigators will get a rare second-by-second look at just what happens -- to the jet and to its occupants -- when something goes terribly wrong midflight.

This study could improve aviation safety, just as automotive crash-test dummies have for decades led to safer cars and fewer fatalities on the road. Scientists plan to mine the test results for at least a decade, writing reports and sharing the information with government regulators and industry representatives to make the 2.8 billion flights taken worldwide each year a bit safer.

The crash was modeled on others in which a plane lost speed and power just before touching down hard, then breaking into pieces. In this test case, after the crew parachuted out, another pilot flew the plane by remote control. The remote pilot slammed the jetliner into a dry lake bed at 140 mph after it had descended more than twice as fast as a fighter jet landing on an aircraft carrier. 

Though the pilots could have survived this test crash, scientists found that flying in first class would have been fatal. Passengers in the middle of the cabin might have suffered concussions and broken ankles, while those in the rear could have walked away. Experts emphasize that the fatalistic view of many airline passengers -- the belief that if a plane crashes, you're unlikely to survive -- ignores data that show the great majority of people in such incidents actually live.

"The chances are that if you're in a crash, you will survive," says Tom Barth, an investigator with the National Transportation Safety Board who studied the crash's impact on occupants of the plane.

But to survive or limit injuries, the Curiosity test case reinforced the importance of bracing for a crash and knowing how to exit a plane during an emergency. While many passengers ignore flight attendants' safety presentations, scientists say the experiment illustrated why the warnings are critical when it's go time.

"We're not trying to scare anybody here," Hansman says. "But the more we understand them, the more we can do to make airplanes even better in the future."

Scientists in biomedical engineering, crash forces and aeronautics had planted sensors and 15 test dummies throughout the plane to measure what happens to people and equipment in the crash of a big commercial jet. They recorded footage of the crash from all angles.

"It is always quite humbling to see the level of destruction in an accident," says Anne Evans, a former senior crash investigator for the United Kingdom's Air Accidents Investigation Branch. Evans, who worked on crashes including Pan Am Flight 103, which blew up in 1988 over Lockerbie, Scotland, killing 270 people, still marvels at the destruction. "Nothing looks as it did before the accident."

'A rough ride'

The plane took off from Mexicali airport with six people aboard. The flight plan resembled a fish hook at speeds up to 184 mph and 6,000 feet in altitude. After about 60 miles, the first officer and flight engineer parachuted out, each in tandem with a jump master. After another 20 miles, Capt. Jim Bob Slocum banked the plane into a slow right turn wide to the north.

Slocum and another jump master left the cockpit 8 miles from the crash site, at 4,000 feet in altitude, when Chip Shanle, a former Navy test pilot who works for American Airlines, took over flying by remote control. Shanle then powered down the wing engines to nearly idle and finally, the tail engine to idle, to slam the plane into the desert floor with its wings level. 

The plane was going 140 mph at impact, which is close to regular landing speed. But the 727 was descending at 1,500 feet per minute, much faster than the 10 to 20 feet per minute of a typical airliner landing.

Shanle watched from a chase plane above as the cockpit tore away from the body of the plane and collided with its left wing on impact. The flight engineer would have died, he says, but the pilot and co-pilot might have survived.

"You knew they were getting a rough ride in there," Shanle says.

He says the crash was similar to one July 19, 1989, of a United Airlines flight in Sioux City, Iowa. That plane's tail engine failed on a flight from Denver to Chicago, and the plane crashed in a fireball and broke into pieces with the cockpit separating. But while 111 people died in that crash, 185 survived.

"The cockpit tore off the same way, and there were three pilots in the cockpit, and they all three survived," he says.

Interior cameras in April's intentional crash capture a chaotic scene of carry-on luggage spilling out of bins and hitting occupants. The plane's lighting and oxygen systems collapsed above the seats toward the front of the plane. Nobody would have survived from Row 7 forward, scientists and investigators found. Seat 7A catapulted 500 feet -- nearly the distance of two football fields -- from the plane.

Luggage bin utility panels have been improved since the 727 was built, but scientists warned that the risks from carry-on luggage remain a concern today because passengers are bringing more and heavier baggage to avoid fees.

The view out one window shows the right landing gear hurtling past at 140 mph, after the tire left a black scar on the fuselage. In a British Airways crash in 2008 that Shanle says was similar to this intentional crash, a passenger suffered a broken leg when the landing gear penetrated that fuselage. But landing gear beneath the wings is designed to shear off in a crash, to avoid puncturing fuel tanks. The fuselage remained largely intact for passengers. And the seats remained in place.

"The good news for the aircraft manufacturers is that everything performed as designed," Shanle says.

The experiment confirmed the soundness of the plane's design, according to Barth and John Hansman, an aeronautics professor at Massachusetts Institute of Technology. For passengers, it reinforced the importance of wearing seatbelts, bracing for a collision and knowing where emergency exits are in the tangle of debris after a crash.

While none of the results was shocking, scientists were surprised by the lower-back strains put on the crash dummies. The amount of dust that got into the cabin could also prompt new ways to make sure passengers could find an exit in the chaos after a crash.

"You may think you know where the exit is, but suddenly, you are in the middle of a zero-visibility dust cloud. Can you find the exit?" Hansman asks. "Things like that in terms of improving aviation safety may be the most lasting thing."

Why the 727?

This wasn't the first time a plane was intentionally crashed for research purposes. On Dec. 1, 1984, NASA and the Federal Aviation Administration crashed a Boeing 720 at Edwards Air Force Base in California to test a fuel additive designed to suppress a fire after a survivable crash.

Manufacturers typically test parts of planes rather than crashing an entire plane, because of the cost involved and the risks and unpredictability of crashing a plane. In the 1984 test case, the left wing hit the ground unexpectedly, and the skidding plane burst into a fireball.

The goal of the Curiosity crash was to break apart the plane while avoiding a fire that would destroy the test equipment and cameras. For $400,000, the program bought a Boeing 727-212 that once carried Bob Dole during his 1996 Republican presidential campaign. The model, which was popular in the 1960s and '70s, was chosen because its cockpit and fuselage are similar to the 737, today's industry workhorse.

The 727 offered another advantage: an unusual rear stairway beneath the fuselage that allowed the crew to parachute out.

"For test purposes, it's the same," Shanle says.

The program's flight plan -- a landing hard enough to break the plane apart without killing everyone -- was designed to mimic a pair of recent crashes:

--The Jan. 17, 2008, crash of a British Airways flight from Beijing to London was blamed on ice blocking the fuel supply less than a minute before the plane touched down. The Boeing 777-200ER hit about 1,000 feet short of the runway, but none of the 152 people on board died. Twelve crew members and 34 passengers suffered minor injuries.

--On Feb. 25, 2009, the crash of a Turkish Airlines flight from Istanbul to Amsterdam was blamed on a faulty altimeter that prompted the autopilot to slow the plane earlier than it should have, and pilots couldn't overcome the problem. The Boeing 737-800 hit tail-first and broke into three pieces a mile short of the runway. Nine people, including three pilots, were killed; 126 survived.

Safer than an escalator

Fatal crashes of commercial planes are rare in the United States. The last one was a Colgan Air flight Feb. 12, 2009, which killed 50 people near Buffalo.

Even in commercial plane crashes with fatalities, the National Transportation Safety Board found 95.7% of all occupants survived such incidents in the USA from 1983 through 2000. In 568 accidents, 2,280 of 53,487 occupants died.

"If you were to take a flight every day, in order for you statistically to be in a fatal aircraft accident, you'd have to live 35,000 years," Hansman of MIT says of the crash rate of 0.2 fatalities for every 1 million airline departures. "There is no other means of transportation that is equivalent in terms of its success. It's actually much safer than riding on an escalator."

Passengers at the front of the test crash would have felt 12 times the force of gravity -- enough to kill someone. The middle cabin experienced eight times the force of gravity, where injuries likely would have included some broken bones. But in the rear, the jolt at six times the force of gravity is comparable to the impact of a bumper car at an amusement park.

Cindy Bir, a professor of biomedical engineering at Wayne State University, set up three $150,000 crash-test dummies with 32 sensors on each. Upright dummies near the front and in the back both suffered severe stress to their lower backs, but the braced occupant didn't, she says.

"Between the lower-spine issue and the vulnerability of sitting upright and having debris flying around, I think the brace position is still the way to go to prevent injuries," Bir says.

Wiring for entertainment fell from the ceiling, creating a web of obstacles. But scientists say furnishings have improved and should leave less debris since a 1981 NTSB report outlined how half the fatal crashes during the previous decade featured failures of cabin furniture.

"You couldn't just move out of the seat to the exit," Bir says. "That fuselage is just filled with dust and dirt and debris."

Where do the experts sit when flying? Shanle, Barth and Bir say crashes are so rare that they still favor first class for the comfort and legroom.

But Evans, the former British crash investigator, prefers sitting in back.

"In terms of relative safety, my view is that the front of the aircraft is more vulnerable," Evans says. "My favored location would be the middle, over the wing, or the rear of the fuselage."

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