Update: Investigators Expected to Quickly Unravel Mystery of Russian Plane Crash

Investigators probing the crash of an Airbus Group SE jetliner in Egypt will focus on how a plane built to withstand extreme turbulence and equipped with devices meant to prevent flight maneuvers that might break it apart could have been ripped to pieces in midair.

With the spread of wreckage across the desert suggesting a high-altitude disintegration that could stem from structural failure or an on-board explosion, Russian carrier Metrojet said Monday that early evidence points to some sort of “mechanical impact.” The U.S. said there’s no direct evidence of a terror link.

Authorities analyzing Saturday’s crash have an advantage over recent high-profile probes, with the impact zone readily accessible, the debris field unencumbered by jungle or water and flight recorders already recovered. Taken together, those factors could greatly ease the complex task of explaining the loss.

“They’ve got the wreckage, they’ve got the recorders, they’ve got the air-traffic-control recordings,” said Paul Hayes, safety director at London-based aviation consultancy Ascend Worldwide. “Assuming the recorders are in good condition they should have initial views within a week.”

The twin-engine A321 jet plummeted to the ground 23 minutes after leaving the Red Sea resort of Sharm el-Sheikh on a flight to St. Petersburg, killing all 224 people aboard. Wreckage was found in an area about 8 kilometers long and 4 kilometers wide (5 miles long by 2.5 miles wide), suggesting a high-altitude breakup, Alexander Neradko, head of the Russian Federal Aviation Authority, said in an interview with Rossiya-24 state television.

Specialists from France, where Airbus is based, may have to help Egypt analyze the recorders, Neradko said, adding that one of the devices had suffered some damage. Investigators from Germany, where the A321 was built, and Ireland, where it’s registered, are also involved, as is Airbus. The team could include authorities from U.S. because the plane’s engines were made by a group led by United Technologies Corp.’s Pratt & Whitney arm.

Cruising Altitude

Metrojet said Monday that there was no evidence to suggest that the crash had stemmed from a maintenance issue, pilot error or a systems failure.

“It could have been anything,” Alexander Smirnov, deputy general director for Kogalymavia, known by the Metrojet brand, told reporters at a briefing in Moscow. “The only reasonable explanation may be a mechanical impact on the aircraft.” He declined to comment on the possibility of a terrorist attack.

In Washington, Director of National Intelligence James Clapper said there’s no immediate indication that the crash resulted from terrorism, while adding that the U.S. doesn’t rule out the ability of Islamic State to shoot down airliners.

While IS’s Sinai affiliate claimed responsibility for downing the plane, Egyptian and Russian officials said those claims weren’t credible. Only the most sophisticated ground- based missiles can reach 31,000 feet (9,450 meters), the cruising altitude at which the Metrojet encountered problems.

Clapper said though that Islamic State has “a very aggressive” presence in Sinai, and when asked if the group could shoot down a plane said: “It’s unlikely but I wouldn’t rule it out.”

No Contact

The plane probably broke up after reaching a cruising altitude of 31,000 feet (9,450 meters), slowing abruptly before falling, Kogalymavia’s Smirnov said. The crew didn’t make any attempts at emergency radio contact.

The easily accessible wreckage and intact recorders contrast with the scenes of other high-profile crashes. After Air France Flight 447 disappeared over the Atlantic en route from Brazil to Paris in 2009, the search for the recorders took two years. In the case of Malaysia Air Flight 370, which went missing two years ago, the wreck has yet to be located, except for a piece of wing. And with Flight MH17 over Ukraine, the probe was hindered by conflict that limited access to the site and possibly contributed to evidence being tampered with.

To find out what happened in Egypt, investigators will start by listening to the cockpit voice recorder. The more complex task will lie in synchronizing those sounds with information from the flight-data recorder to piece together what happened. Egyptian authorities have said they have the equipment required to do that decoding.

Small Device

If the aircraft did indeed break up at midair, investigators will be looking at causes of similar crashes such as bombs, missiles, on-board explosions and structural failures.

“It’s very hard to pull one of these things apart in flight. Very hard,” said John Cox, a former U.S. airline pilot who has participated in accident investigations.

While a missile attack on the jet seems unlikely, a bomb like the one that detonated on Pan Am Flight 103 en route from London to New York over Lockerbie, Scotland, in 1988 may be more plausible. A small device smuggled in checked luggage blew out the side of the Boeing Co. 747, according to the U.K.’s Air Accidents Investigation Branch report.

So far, neither Egyptian nor Russian officials have said there’s any evidence of a bomb. Explosive devices cause telltale pitting on nearby metal and also leave chemical residue, according to the U.S. National Transportation Safety Board, so an examination of the wreckage should tell investigators whether or not that was the cause.

Tail Strike

One area investigators will pay close attention is damage to the A321 when its tail struck the runway while landing in Cairo in 2001. The plane was repaired and returned to service, according to London-based Ascend Worldwide Ltd., which gathers data for insurers.

There have been at least two accidents caused by improper fixes to tail damage. China Airlines Flight 611 flying from Taiwan to Hong Kong broke apart in 2002, killing all 225 people aboard a Boeing 747 that was repaired 22 years earlier, while Japan Airlines Flight 123 hit a mountain in 1985 after a repair came apart, claiming 520 lives.

In both cases, part of the structure that holds in air at high altitudes, known as the aft pressure bulkhead, was damaged when the planes scraped the runway. Photos of the wreckage in Egypt appear to show that the tail section fell separately from the rest of the plane. Metrojet rejected the idea that botched repairs could have caused the crash.

Another cause of midair breakups has been explosions in aircraft fuel tanks, according to Steve Wallace, former chief of the U.S. Federal Aviation Administration’s accident investigation division. TWA Flight 800, another 747, crashed into the Atlantic near New York in 1996 as a result of such an explosion, killing all 230 aboard.

“Unless there’s something that says ‘obvious,’ you generally have to wait until you get the reports from the recorders,” Robert Mann, a former American Airlines executive who is president of R.W. Mann & Co. and an aviation consultant, said in an interview.

–With assistance from Chris Strohm in Washington.