What happens when airlines receive bomb threats?

How threats are assessed

If a threat is considered credible, the crew is informed immediately. The captain makes decisions using a safety checklist, Waites said. On the ground, that can mean evacuating the aircraft; in the air, the priority is to land as soon and safely as possible.

Training and response procedures

Flight crews train through live exercises that cover different threats, including searching for explosives that may have been smuggled aboard. The International Civil Aviation Organization conducts audits to check that guidelines are followed.

When a threat comes by phone, airline employees are told to keep the caller on the line and collect as much information as they can, aviation security expert Philip Baum said. Many of this week’s threats arrived by email, and authorities had enough information to require aircraft inspections.

Costs and wider concerns

Diverting a flight because of a bomb threat or an unruly passenger can cost up to $250,000, Baum said. The expense may be lower in this case because most disrupted flights were short-haul, reducing the chance of overnight delays.

Jacob Funk Kirkegaard, a senior fellow at the Brussels-based Bruegel think tank, said the threats appeared intended to create uncertainty about air traffic reliability across Europe. He also said they could test how quickly and consistently authorities in different countries respond, potentially exposing weaknesses for future attacks.