Drones are great tools for filmmakers and photographers, but they’re not toys to be played with around airports — those gadgets can actually bring airplanes full of passengers down.

That’s why on Tuesday, January 22, flights were temporarily grounded at Newark Liberty International Airport in New Jersey following the sighting of two drones being flown over Teterboro Airport, a small private airport close by. A pilot told air traffic control that one of the drones came within 30 feet of his plane, sparking the 90-minute traffic halt for all outbound and inbound flights.

In a statement, the Federal Aviation Authority said, “At approximately 5:00 PM, we received two reports from incoming flights into Newark that a drone was sighted at about 3,500 feet above Teterboro, New Jersey. At that point, flights arriving into Newark were held for a short duration. Since then, and with no further drone sightings, arrivals have been resumed.”

Drones have become a serious issue for airports lately, with London’s Heathrow Airport forced to delay flights for one hour earlier this month after a drone sighting. Gatwick Airport grounded and diverted more than 1,000 flights between December 19 and 21 after a drone was spotted, impacting the travel of around 140,000 people.

H/T: BBC News