A suspected hijacking in Amsterdam turned out to be a false alarm.
Dutch military police said they were investigating a situation on board a plane at Schiphol airport.
"There is a suspicious situation and that's all I can say," a spokesman for the military police said.
However, the airline later confirmed that the hijack alarm was triggered by mistake, adding that "nothing has happened".
Air Europa said in a tweet on Wednesday night that the scare that sent emergency services rushing to Schiphol was a false alarm.
The carrier says a warning that triggers hijack protocols at airports "was activated, by mistake."
It adds that all passengers "are safe and sound waiting to fly soon. We deeply apologise."
Reports on Twitter suggested three men armed with knives were trying to hijack an outbound flight - and there are suggestions hostages have been taken on board a plane.
Local reports have said the situation has now "been ended", but it is unclear what has happened to resolve the incident.
The incident reportedly took place on board an Air Europe plane to Madrid with at least 27 people thought to be on the flight.
A crew member of the departing flight activated a hijacking alert, according to Dutch broadcaster NOS.
Heavily armed security forces are at the scene, along with multiple ambulances.
Emergency services issued a so-called Grip 3 report. This happens with "an incident or serious event with major consequences for the population", reports De Telegraaf.
Images showed crowds of people in the airport and armed police behind a cordon.
Schiphol Airport's official Twitter account tweeted: "The Royal Netherlands Marechaussee is currently investigating a situation on board of a plane at Amsterdam Airport Schiphol. We keep you posted."
One passenger said: "Masses of people have just been asked to move back further behind the security cordon."
Another passenger told MailOnline: "Nobody knows what is happened here, there was a lot of screaming going on and armed police running about.
"It's quite a frightening experience as we are behind a cordon unable to move for our own safety as police is everywhere."
Schiphol is one of the busiest transport hubs in Europe, handling more than 70 million passengers a year.