Drone sighting temporarily halted departures at Heathrow Airport in London

A British Airways aircraft sits on the tarmac at Heathrow Airport in London

"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".

The flights were halted at 5:05 pm GMT (12:05 pm ET), and resumed about an hour later.

The alleged sighting came four days after both Heathrow and Gatwick airports reported they were investing millions of pounds in equipment to prevent future flight disruption.

Arriving planes however are continuing to land at Heathrow.

Transport Secretary Chris Grayling told Parliament that the Gatwick disruption was "deliberate, irresponsible and calculated, as well as illegal".

Last month, flights to and from Gatwick airport were suspended several times over a three-day period because of similar sightings.

Some 81 airlines serving 204 destinations operate out of Heathrow, located west of London.

More than 140,000 passengers at Gatwick were affected during 36 hours of chaos between 19 and 21 December.

Police have not charged anyone in relation to that incident.

The British army had to be deployed to the airport on December 20 after it grounded all flights.

In the aftermath of the Gatwick incident it was announced that new measures would be brought into place regarding drone exclusion areas around airports, as well as competency tests for people owning drones over a certain size.

The airport is planning for an increase in its capacity of up to an extra 25,000 flights a year before the third runway opens, Heathrow said, as it outlined the latest phase of its expansion proposals.

Heathrow said it was working closely with authorities including the police and looking at relevant technology to combat the threat of drones. Exclusion zones are now one kilometre around airports and will be extended to five kilometres.