- Video report by ITV News correspondent Rebecca Barry
Flights at Gatwick have resumed once more after a suspected drone sighting caused yet another suspension, an airport spokeswoman said.
The airport initially reopened on Friday morning after 36 hours of total shutdown, sparked by a drone flying near the runway and causing chaos for hundreds of thousands of passengers.
Almost 700 flights were scheduled for the day - but at around 5.10pm, another reported sighting meant operations were once again halted, as police said they believe more than one unmanned aircraft was responsible and were investigating the possibility of multiple culprits.
Just over an hour later, an airport spokeswoman said flights had resumed.
"While we investigated, airfield movements were suspended," she said.
"This was a precautionary measure as safety remains our main priority. The military measures we have in place at the airport have provided us with reassurance necessary that it is safe to re-open our airfield.”
But disruption and uncertainty continues for passengers, with a number of flights being cancelled or delayed.
For three days, Virginia Concalves had been sleeping at the airport, taking the morphine she needs for stage four breast cancer in the waiting area.
Her airline has not provided her with a hotel due to what they called the scale of the disruption, and she told ITV News she was too weak to find one herself.
"Very disappointed, because - probably - it's the last time I'll see my family," she said.
"It's not so bad, going through cancer, and then this happens. And I will be still sleeping at the airport until Sunday. What can I do? Nobody cares."
After her story appeared on ITV News, staff at Gatwick Airport arranged a hotel room for Virginia.
Another passenger who tried to check in shortly after 5pm told ITV News of her devastation at learning her planned trip to Norway to see family might be under threat.
"I'm so gutted - I've been looking forward to this for so long," she said.
Transport Secretary Chris Grayling previously confirmed military equipment was being used to stop further drone disruption.
He said there had been around 40 sightings of what were thought to be a "small number of drones" while the West Sussex airport was closed.
The reopening came despite no confirmation from police that a drone had been brought down, or that there had been any arrests.
Disruption was expected to continue into the weekend even before the latest sighting.
Flights in and out of the airport were first suspended on Wednesday night, with the shutdown continuing throughout Thursday despite a brief reopening in the early hours.
Some 120,000 passengers due to fly into or out of Gatwick during that time were left unable to travel, while many inbound flights were diverted to alternative airports as far away as Amsterdam and Paris.
Asst Ch Cons Steve Barry, from Sussex Police, said officers were working on the assumption that there was more than one drone being used.
"In terms of how many perpetrators, there's a number of lines of inquiry, there's an ongoing investigation, we're pursuing that trying to find out who has been responsible for this really malicious criminal behaviour," he said.
He said there had been no opportunities to shoot down the drones, explaining: "We have to consider whether it's safe to do so, it has to be dynamically assessed at the time, in terms of the risk, and we have to assess whether it's going to be efficient, effective, how likely it's going to be we're going to be able to take the drone out.
"I have to say on the range of options we've got available, shooting the drone out of the sky is probably one of the least effective options. It doesn't mean to say it's impossible, which is why we've got the option available to us should the option become available."
Mr Barry said the drones could have been operated from a fair distance away, but police are focusing on "likely locations in and around the airport".
Addressing the problems with identifying suspects, he added: "It's the remoteness between the officer and the drone and over the whole area around Gatwick does make it really difficult to link the drone to the operator."
Speaking on BBC Radio 4's Today programme, Gatwick's Chief Operating Officer Chris Woodroofe said a number of "mitigating measures" had been put in place to allow the airport to reschedule flights on Friday morning, despite the drone not being found.
Asked if the "mitigating measures" meant the drone would be shot down, he said: "You'll appreciate that there are certain things I can't talk about in detail."
Speaking on Thursday, 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.”
Sussex Police added that they have a "a number of options" around the airport's perimeter to help prevent further disruption, following an "unprecedented" number of drone sightings on Wednesday night and throughout Thursday.
On Thursday night, police revealed there had been more than 50 sightings of the drone in the 24 hours from 9pm on Wednesday, when the airport first closed.
Detective Chief Superintendent Jason Tingley, of Sussex Police, had said that firearms officers could be used to "take the drone out of the sky and remove that disruption so we can get Gatwick back to normal".
Previously, the option of shooting the drone down had been ruled out over a fear of stray bullets.
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.
- Why does a drone cause so much chaos?
Mr Grayling also called the incident "unprecedented" and said lessons would have to be learnt "very quickly from what's happened".
Speaking on BBC Breakfast, he continued: "I plan to convene discussion with other airports around the UK very quickly indeed so that they know what's happened, they understand what lessons need to be learned, and we've put in place every measure we possibly can to ensure this can't happen again."
Mr Grayling said the disruption was caused by "the same small number of drones seen many times" and there was "no evidence" to suggest it was "terror-related", but it was "clearly a kind of disruptive activity that we've not seen before".
The incident led to calls for more action to tackle illegal drone use.
The runway was closed almost constantly after two drones were spotted being flown inside Gatwick's perimeter.
It was reopened at 3am on Thursday but shut again 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.
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.