All 78 automatic passport gates at Schiphol went down at around 6am on Sunday 18 October, leaving hundreds of passengers stranded and thousands more stuck in long queues.
The Royal Marechaussee, the military police in charge of border control, blamed an IT fault and said it had seen no sign of a cyberattack.
It is still investigating the exact cause but will not publish the results, citing operational reasons.
Manual checks
Every passenger travelling to or from a country outside the Schengen area, transit passengers included, had to be checked by hand.
The Marechaussee staffed all its desks and made checks less thorough to speed things up, yet Schiphol said the average wait was an hour, with some people queuing for an hour and a half.
The gates were back in service by around 3pm.
Compensation
KLM held flights where it could, Transavia offered flexible rebooking, and the Marechaussee told anyone who missed a flight to contact their airline.
Compensation looks unlikely, as experts expect the outage to count as force majeure because the gates are run by the Marechaussee, not the airlines.
Planning your next trip through Schiphol? Check out our practical guide to the airport.