U.S. aviation authorities are reviewing security for passenger planes at overseas airports as consensus grew Thursday that a Russian jet likely crashed in Egypt because a bomb was slipped aboard before takeoff.
No U.S. airlines fly in to, out of or over the Sinai Peninsula, where Metrojet Flight 9268 crashed Saturday, killing all 224 people on board. But the crash could expose holes in security measures at overseas airports where U.S. airports do operate, security analysts and members of Congress said.
"If this is a bomb, it shows the weaknesses that can be there," said Rep. Peter King, R-New York, who received a classified briefing on the crash as a member of the House Intelligence Committee.
"It's even more so with planes leaving from overseas and you have American passengers on them," King said.
Even President Barack Obama said in a radio interview Thursday that "there is a possibility that there was a bomb on board, and we're taking that very seriously."
But U.S. military and diplomatic officials, as well as lawmakers who'd been briefed, continued to stress Thursday that it hadn't been conclusively established that a bomb brought down the Airbus A321 — mechanical failure remains on the table, they said.
"While it hasn't been confirmed officially, there are intelligence reports that it is likely that this could have been a bomb placed on the airplane by ISIS, and that is our grave concern at this point in time," said Rep. Michael McCaul, R-Texas, chairman of the House Homeland Security Committee.
"The idea that ISIS now would have the capability to target aircraft — if, in fact, this is the case — would be the most significant terrorist attack against the aviation sector since 9/11," McCaul said on MSNBC's "Andrea Mitchell Reports."
It's worth noting that some consider the downing of Malaysian Airlines Flight MH17 over Ukraine in 2014, killing 298 people, an act of terrorism.
King said, "I can’t go into all the details, but I think there is a consensus building around the world that there was an explosive, and, obviously, if there was, then ISIS would certainly be a prime candidate."
And if that supposition proves true, McCaul said, it would be "a major threat to airlines that could be flying into the homeland."
McCaul noted that the airport at Sharm el-Sheikh, from which the Metrojet flight took off Saturday, didn't impose security measures meeting U.S. standards because no U.S. airlines currently fly there.
Foreign airports where U.S. airlines do operate are required to comply with Transportation Security Administration regulations, but without direct oversight from the TSA — which McCaul and others said was a concern.
"Having said that, TSA is reviewing their procedures to see if we can't just ramp up and have heightened security at all these key hotspot airports," McCaul said.
Evidence for an ISIS bomb began emerging publicly Wednesday, with U.S. and British officials and sources in the region telling NBC News that data both from the crash scene and from intelligence operations pointed in that direction.
Related: Suspicion of ISIS Bombing in Sinai Jet Crash Could Bring Strong Russian Retaliation
Investigators in Egypt are reviewing information from the plane's flight data recorder — one of the jet's "black boxes" — and from its cockpit voice recorder, Egyptian aviation officials told NBC News.
One of the officials said the cockpit recorder is "partially damaged" and that "a lot of work is required in order to extract data from it."
