An IT failure knocked out the electronic passport gates at Amsterdam Airport Schiphol on Sunday, and hundreds of travelers missed their flights, NOS and NH Nieuws reported.

The outage began at about 6 a.m. local time, NOS and NH Nieuws reported. All 78 e-gates went down, NOS reported. NH Nieuws put the number at nearly 80.

With the gates down, officers of the Royal Netherlands Marechaussee, the Dutch border police, had to check every traveler by hand, NOS and NH Nieuws reported. NOS reported that the force sent in extra staff so that every desk was open.

Long lines formed. Travelers waited about an hour on average, and some waited up to an hour and a half, NOS and NH Nieuws reported. The airport was busier than usual because of the autumn school holiday, NOS and NH Nieuws reported.

Several hundred people missed their flights because of the outage, a Schiphol spokesperson said, NOS, NH Nieuws and NU.nl reported. NU.nl reported that KLM held some flights for about 15 minutes.

The gates later came back into use, NOS and NH Nieuws reported. The Marechaussee said the cause was an IT failure, NOS and NH Nieuws reported. A spokesperson said it was not a cyberattack, NOS reported. The exact cause is still being looked into, NOS and NH Nieuws reported.

Airlines tried to help. KLM held flights for passengers as much as it could, and Transavia said it would be extra flexible with rebooking, NOS reported.

The e-gates can be used by travelers age 14 and older from the European Union and the Schengen area, NOS reported. People from the United Kingdom, the US and South Korea, among others, can also use them. Travelers scan their passport and then look straight into a camera.

What we know: An IT failure took the e-gates offline on Sunday morning, and hundreds of travelers missed flights.
What we don't: What exactly caused the IT failure.