It added it first received the reports at about 5:05 p.m. Tuesday.
"It is crucial that our plans maximise the benefits of expansion across the country, including for the communities closest to us", said Emma Gilthorpe, Heathrow's Executive Director for Expansion. "We apologise to passengers for any inconvenience this may cause".
She explained: "Heathrow's aim is to design a sustainable, fair and more efficient future airport while connecting the United Kingdom to global growth".
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The incident comes just weeks after London's second busiest airport, Gatwick, was severely disrupted when drones were sighted on three consecutive days in December.
Heathrow said in a statement: "Based on standard operating procedures, working with Air Traffic Control and the Met Police, we have resumed departures out of Heathrow following a short suspension".
Arriving planes, however, are continuing to land at Heathrow.
"We've been sitting on the runway at Heathrow for like an hour and a half", another person said.
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Ministers are now exploring the use of military grade jammers and blocking systems to bring down rogue drones, such as the Israeli Drone Dome system reported to have been deployed at Gatwick.
"I have already spoken to both the Home Secretary and Defence Secretary and the military are preparing to deploy the equipment used at Gatwick at Heathrow quickly should it prove necessary".
A senior detective also said at one point it was possible drones hadn't flown over the airport, sowing confusion, but police later insisted the drone sightings were authentic. When a drone collided with a passenger plane over Quebec City, Quebec, last year, the plane landed safely.
Police could also fine drone users failing to comply with authorities or present registration to operate a drone up to £100.
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