Shooting down the drone causing chaos at Gatwick Airport is now a "tactical option" being considered by police as bosses weigh up when to reopen the runway.
Detective Chief Superintendent Jason Tingley, of Sussex Police, said there had been more than 50 sightings of the device since the airport was first closed on Wednesday.
He said that shooting the drone down was now an option after other strategies failed as fury over the crippling delays grew further still before the shutdown entered a third day.
Speaking to reporters outside the airport's South Terminal, he said: "We will do what we can to take that drone out of the sky and remove that disruption so we can get Gatwick back to normal.
"One of the options is to use firearms officers if that presents itself - they have been out on the ground today and that's a consideration and a tactical option that's open to us.
"There are a number of factors in terms of range, the height of the drone and the likely impact on us firing at the drone but that is a tactical option open to the gold commander who will make a decision based on the information available to them at the time."
Mr Tingley added police were working on the assumption the drone had been modified, with the "intent of causing disruption", and were looking through CCTV to identify the make and model.
He said they were following up a "number of persons of interest" in their investigations, with the military drafted in to offer additional support to officers.
According to reports, one line of inquiry was that a lone wolf eco-warrior was behind the attack.
Chris Woodroofe, Gatwick's chief operating officer, said 120,000 passengers' flights had been disrupted.
Mr Woodroofe said the airport could remain closed for potentially all of Friday after drone activity was spotted again on Thursday night.
He told reporters: "My apologies to all those passengers who have seen this disruption from the criminal activity from these people who are purposely disrupting our airport and their travel so close to Christmas."
Mr Woodroofe added: "We have had the police, we have had the military seeking to bring this drone down for the last 24 hours and to date that has not been successful so Gatwick Airport is still closed.
"It is closed for the rest of this evening and our intention is to review on an ongoing basis whether we can reopen tomorrow.
"But we are working up contingency plans all the way through to no flights tomorrow."
Mr Woodroofe refused to comment on the possibility of the airport awarding compensation to passengers who had been affected by the chaos
He added: "The issue from my perspective is that this has been a criminal act purposefully undertaken in order to cause this disruption and I very much hope we bring the perpetrator to justice."
The incident led to calls for more action to tackle illegal drone use.
The runway has been closed almost constantly since two drones were spotted being flown inside Gatwick's perimeter at 9pm on Wednesday.
It was reopened at 3am on Thursday but was closed 45 minutes later after the drones re-emerged.
Transport Secretary Chris Grayling said there was no known motive for the pilot of the "commercial" drone.
Night-flight restrictions will be lifted at other airports - probably those which serve London - so that "more planes can get into and out of the country"
"Apologies for the residents affected, but it's right and proper that we try and sort people's Christmases out," Mr Grayling said.
Passengers faced severe disruption as flights were unable to leave the tarmac at Gatwick, while many inbound flights were diverted to alternative airports as far away as Amsterdam and Paris.
Additional reporting by the Press Association.
