Thousands of passengers flying to and from Amsterdam’s Schiphol Airport suffered delays and cancelled flights Wednesday because of problems refuelling planes that crippled the busy European aviation hub for hours.

Airport spokeswoman Willemeike Koster said 180 flights were cancelled at the airport just outside Amsterdam, stranding passengers at Schiphol and other airports. Field beds were set up at the airport as a precaution in case passengers were forced to wait overnight for their flights, Koster told The Associated Press.

It wasn’t clear how many passengers were affected by the delays and cancellations, but Koster said the number ran into the thousands.

The problem began in the early afternoon and was finally fixed hours later. Schiphol announced around 10 pm (2000 GMT) that the fuel delivery system had restarted. Spokeswoman Madelon van der Hof said that aircraft were being refueled and departing as the airport gradually began returning to normal operations.

The airport said earlier that a company that supplies fuel to planes at the airport had “a fault in their system. That means that planes cannot be refueled right now, which is causing delays.”

Schiphol warned earlier that the problem could last deep into the evening and said it regretted the inconvenience for travellers and airlines.

The exact nature of the problem wasn’t immediately clear.

Before the system was successfully restarted, only one-third of the usual number of flights was arriving at Schiphol on Wednesday night, Koster said. Even fewer were leaving.

“If they have enough fuel they can go,” Koster said. “There are planes departing, but it is at a minimum level.”

Dutch airline KLM said it was possible flights would be cancelled Thursday as well due to a “phased restart” of operations at the airport.

The fuel problem came during the busy summer vacation period in the Netherlands and on a day that saw a heat wave set a record high temperature. The Dutch weather service Weerplaza said the southern city of Eindhoven reported a temperature of 39.3 C (102.7 F), the hottest day in the country in 75 years.

Airport spokesman Hans van Kastel told Dutch broadcaster NOS that the fuel issue wasn’t believed to be linked to the hot weather.