US travelers were stranded at Newark Liberty International Airport on Labor Day after an equipment outage caused numerous flight delays and cancellations.

The Federal Aviation Administration (FAA) announced that it had implemented ground delays at the New Jersey hub on Monday afternoon due to a “radar issue,” NBC New York reported.

According to Flight Aware, this resulted in at least 456 delays and 64 cancellations of both inbound and outbound flights.

Some airlines were even forced to divert planes to other airports while many passengers learned of the delays while seated in planes on the runway, Pix11 reported.