Experts believe military-grade devices to detect and jam radio control signals were used after one runway at Britain’s busiest airport was shut temporarily following a drone sighting.
Scotland Yard said a “full criminal investigation” had been launched. Officers were among those to have spotted the drone.
Departures were suspended for about an hour at the airport, with Heathrow describing the move as a “precautionary measure” to “prevent any threat to operational safety”.
The authorities have refused to discuss tactics in detail, with government officials saying the information was classified.
However, Metropolitan Police Commander Stuart Cundy confirmed military assistance had been brought in.
A Ministry of Defence spokesman added: “We are deploying specialist equipment to Heathrow Airport at the request of the Metropolitan Police.”
It comes after thousands of passengers were caught up in three days of disruption at Gatwick last month following reports of drone sightings. The importance of the role played by the Armed Forces in enabling flights to recover at Gatwick is emerging only now.
Transport Secretary Chris Grayling called in the military again within minutes of the Heathrow sighting yesterday.
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A conference call of government ministers from the Transport department, MoD, Home Office, as well as London Mayor Sadiq Khan and the Met Police, approved the deployment.
A source said: “It was pretty swift. Not only the equipment but the people needed to operate it were moved to Heathrow very quickly.”
Mr Cundy said the drone was spotted just after 5pm. “Military assistance has been implemented to support us,” he added.
“However, we will not be discussing in any further detail the range of tactics available to us as this would only serve to potentially undermine their effectiveness.
“Police officers were among those who saw the drone and a full criminal investigation has been launched. We are carrying out extensive searches around the Heathrow area to identify any people who may be responsible.”
The Government is planning laws to let airports use military equipment in future, including missiles.