A deadly plane crash in Pakistan is prompting questions about how the crew could touch down without landing gear when their sophisticated jetliner was bristling with equipment to prevent pilots from doing just that.


After an abrupt descent that had unnerved air-traffic controllers, the pilots of the Pakistan International Airlines Corp. jet on Friday briefly put the aircraft on the runway without the landing gear, grinding along on its two engines at a speed of more than 327 kilometers (203 miles) per hour, according to preliminary data.


The pilots aborted the landing attempt, climbing back into the sky, but reported shortly afterward they’d lost power. The Airbus SE A320 apparently glided into a neighborhood as pilots were attempting to return to the same runway, killing 97 of 99 people aboard.


“It is unbelievable to me that an airline crew on a jet like an Airbus, with all the warning systems, would attempt to land the plane without the gear extended,” said John Cox, an aviation safety consultant who formerly flew the A320 as a U.S. airline pilot.


In addition to checklists designed to make sure pilots don’t attempt to touch down without the landing gear, the jetliner has multiple warning systems designed to alert crews if they somehow forget or the gear aren’t working.


“The airplane is not happy that you’re this close to the ground without the gear extended,” said Cox, who is president of consulting company Safety Operating Systems.


It’s not yet clear why the two jet engines quit after functioning well enough for about two minutes to lift them about 3,000 feet (915 meters) above the runway. Engines have become so reliable that losing two at the same time is almost always because of some common factor, such as damage from hitting a runway or a problem with the fuel supply.


Regardless, the bizarre landing attempt — which was carried out without any indication from the crew that they’d had an emergency during their initial descent — either triggered the accident or was a catalyst that worsened the situation, according to Cox and others who have studied crashes.


A Pakistan International spokesman declined to comment on “incomplete information.” An Airbus spokesman referred queries to Pakistani authorities. Civil aviation spokesman Abdul Sattar Khokhar didn’t respond to a call on his mobile phone.


As Flight 8303 from Lahore approached Karachi’s Jinnah International Airport last Friday afternoon, air-traffic controllers were concerned that it wasn’t descending on the proper path, according to a report cited by Sky News. A controller cautioned the pilots that they were “high” and urged them to adjust, according to the leaked preliminary report.


Turn Back

“We are comfortable. We can make it,” the pilot can be heard telling the controller, according to a recording of Karachi’s air-traffic radio posted on the LiveATC.net website.


Twice as the plane neared the runway, a controller told pilots to turn and break off their approach, according to the report. Again, the pilot declined, responding on the radio he was “comfortable” and was prepared to land on runway 25-Left.


At no point did the pilots say they had a problem with their landing gear or any other type of emergency, according to the radio calls.


Approaching a runway with such a rapid descent, which often leads to higher-than-recommended speeds, is a harbinger of danger, according to decades of warnings from investigative agencies such as the U.S. National Transportation Safety Board and the nonprofit Flight Safety Foundation.


After the controllers finally cleared the plane to land — despite their earlier warnings — the pilot replied, “Roger.” In the background, the sound of a cockpit warning chime can be heard.


Too Much Energy

The jetliner was well above the normal speed as it neared the runway, said Jeffrey Guzzetti, the former chief accident investigator for the U.S. Federal Aviation Administration. It was traveling at roughly 250 miles an hour at about 1,000 feet above the ground, according to the tracking website, Flightradar24.


That’s more than 50 miles per hour faster than is typical for jets like the A320, Guzzetti said.


“They have too much energy for a normal landing,” he said.


It not only increases the chances of skidding off the runway, but puts additional pressure on the pilots to slow the big jet and can lead to other things going wrong.


Flightradar24’s data suggests that the jet was traveling at 375 kilometers (233 miles) per hour when it reached the runway and slowed to about 327 kilometers per hour as it lifted off. The data hasn’t been validated by investigators.


The airline said Thursday that the cockpit voice recorder, a key to piecing together the events, had been found in the debris from the wreckage. The flight data recorder was located earlier.


While it’s possible that in the chaos and confusion they might have have forgotten about the landing gear, it’s still puzzling, according to Guzzetti and Cox.


Computer System

The A320’s on-board computer system issues both a warning sound and illuminates a light to draw attention to a text message if the gear isn’t out as the plane nears the ground.


A separate safety system designed to prevent aircraft from inadvertently striking the ground also senses when the gear isn’t deployed before landing. Its recorded voice repeatedly says “Too low, gear” if the problem continues.


Before-landing check lists also require crews to verify that the plane’s instruments show the gear is locked into place.


“It’s very unusual in modern transport category aircraft to have a no-gear landing, just because the checklist and the warnings that go off,” Guzzetti said.


At about 2:34 p.m., the plane slammed onto the runway. Its engines left a series of black smudge marks, starting at 4,500 feet from the start of the landing strip, according to video of the runway broadcast by news outlets. It shows three separate patches, as if the plane skipped into the air between impacts.


“Going around,” a pilot on the jet told controllers, the term for aborting a landing and taking off again.


The plane climbed about 3,000 feet, but couldn’t hold its altitude, according to the radio transmissions and flight data.


“Sir, we have lost engines,” a pilot said. Then, 30 seconds later, he said, “Mayday. Mayday. Mayday.”


Seconds later, the plane hit the ground.