But if they do know what caused the crash, they are not saying.
The Russian Metrojet plane disappeared from radar on Saturday over Egypt’s Sinai Peninsula about 20 minutes after it took off. It had reached a high altitude, officials said. It was flying from a vacation town in Egypt to St. Petersburg, Russia.
The plane broke apart in the sky, officials said. All 224 people on board died.
Nearly all the passengers were Russian tourists. Three Ukrainians were also among the dead.
The crash was the worst in Russia’s flying history.
Emergency crews have recovered both the plane's black boxes. The boxes record flight data and pilot communications. The information on the black boxes has not yet been released.
Airline says the plane and crew are not to blame
A top Metrojet official rejected the idea that a 2001 repair to the plane's tail could have caused the crash. However, poor repairs to older planes have caused similar crashes.
No technical failures could cause a plane to break up in the air, Metrojet’s deputy director told reporters in Moscow.
"The plane wasn't flying, it was falling," Aleksander Smirnov said.
Smirnov pointed out that the crew lost total control. No one on the plane called for help. He said the crew did not make a mistake.
Smirnov said the only way to explain the crash is "some kind of external action."
But Russian government officials say it is too early for the airline to know if technical failure or human error might have caused the crash.
Terrorism?
The New York Times newspaper noted that Russia recently sent troops into Syria. Those troops defend President Bashar al-Assad and attack his opponents. They also attack the terrorist group, Islamic State.
That military action has made some call for a global jihad against Russia.
Militants who say they are linked to the Islamic State claim they shot down the plane. But aviation and military experts say they believe the group does not have missiles that could reach the plane's altitude of 9,100 meters.
James Clapper, the U.S. director of national intelligence, said Monday that "we don't have any direct evidence of any terrorist involvement yet'' in the crash.
But he noted that the Islamic State group has a significant presence in Egypt's Sinai Peninsula.
A spokesman for Russian president Vladimir Putin said officials were considering all ideas about what might have caused the crash. That included a terrorist attack, he said.
Meanwhile, investigators continue to examine the crash site and gather information. And, some airlines – including Air France, Lufthansa, Emirates and Qatar Airways – say they will stop flying over the Sinai Peninsula for safety reasons.
Words in This Story
external – adj. coming from outside
aviation – n. the business or practice of flying airplanes, helicopters, etc.
altitude – n. the height of something (such as an airplane) above the level of the sea