Departures were halted after the sighting of a possible drone in the vicinity of the airport just after 5 p.m. Tuesday, according to the Metropolitan Police. Services restarted after an evaluation of the threat to operational safety.

The incident spurred concern that Heathrow had been targeted for disruption after drone raids on London’s Gatwick hub ruined travel plans for more than 150,000 people before Christmas. That event raised questions about the preparedness of airports for encroachment by drones into commercial airspace.

Heathrow said it had halted outbound flights as “a precautionary measure” and apologized to passengers for the inconvenience caused. The location of the drone sighting meant arrivals weren’t impacted, a spokeswoman said.

Transport Secretary Chris Grayling said on Twitter that he had consulted with Home Secretary Sajid Javid and Defence Secretary Gavin Williamson and the military would deploy the same equipment that allowed the resumption of flights of Gatwick, if necessary.

Read More: Gatwick Drone Raid’s Legacy of Lost Fees, Fortified Airports

Heathrow may be better able to cope with drone disruption as it has two runways to Gatwick’s one. While two people were questioned by police about the earlier incident, no-one was charged and the investigations continue. DM