Two explosions, one of them reportedly caused by a suicide bomber, ripped through Brussels' Zaventem airport on Tuesday, killing 11, according to Belgian officials.
A spokesman for the Brussels Metro said 15 people were killed and 55 injured in an explosion on a train later, The Associated Press reported.
At the airport, the blasts tore through the public reception area where people gather to check in and see their loved ones off or welcome them back.
Video footage shows smoke billowing from the airport after the blasts and people running away from the scene.
Even if the area after security is obviously harder to get to with explosives, aviation security expert Julian Bray told Mashable on Tuesday thateverybody is under observation from the moment they step inside an airport.
In addition to uniformed officers, plainclothes security patrol the public reception area in most airports, and security monitor surveillance cameras in real time.
"But, obviously, if an explosive device is packed into a bag or suicide vest, that makes it very difficult to detect," Bray said.
See more from the terrifying attacks:
Bray described Brussels's airport as "very secure" and said law enforcement personnel was likely present at the time of the attacks.
"It's the EU capital with a high number of politicians and officials going through daily," he said, "so security has always been high."
Brooks Tigner, editor of Security Europe and EU and NATO affairs correspondent for Jane's Airport Review who is Brussels based, heard and felt the metro explosion which took place after the airport attack.
He told Mashable that the airport attack will no doubt force EU authorities to rethink airport security.
"The big question now is if [attackers] are going to target public departures areas, what do we do?" he said.
"Will authorities have to [install detection systems] on the arrival deck outside? Or move security to the public receptions hall? Will they start doing one-by-one check-in?" he added. That could mean "queues, queues, queues" and having to arrive at the airport three or four hours ahead of a flight instead of two.
Bray echoed Tigner's remarks, saying if authorities implement too many security measures, "you would literally strangle everything."
As an example, he cited London's Gatwick airport, which recently started searching trucks on the approach to the terminals.
But that may be the route European authorities have to take.
"It becomes a question about stepping up security versus the freedom of movement of people," Tigner said. And after Tuesday's attack Europe is likely to "shift to security."
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