Flights at Gatwick Airport have again been suspended because of a suspected drone sighting, prompting further passengers to be stranded after planes were grounded for around 36 hours.
The airport said operations were halted on Friday evening after a sighting at around 5.10pm.
The runway had been reopened in the morning after planes were stopped from flying in and out of the airport from 9pm on Wednesday.
Gatwick Airport has reopened again at 6:30pm after operators were reassured that military measures now in place mean it is safe to fly despite a "confirmed sighting of a drone", a spokeswoman has said.
Police believe more than one unmanned aircraft are responsible and are investigating the possibility of multiple culprits.
On Friday evening, a Gatwick spokeswoman said: "We have currently suspended airfield operations as a precaution due to a suspected drone sighting."
A Sussex Police spokesman said flights were being grounded after "unconfirmed reports" of a fresh sighting.
'High-end criminal behaviour'
A sign warning against flying drones near the airport after Gatwick airport is closed again due to a drone sighting.
Police prepared to blast the drones out of the sky with a shotgun or jam them with a hi-tech radar system as they continued their hunt for the aircraft and their operators.
Military equipment was being used to stop further drone disruption while a range of tactics are in place if any unmanned aircraft are seen inside the perimeter.
One piece of equipment believed to have been deployed at the airport is the Israeli-developed Drone Dome system, which can detect drones using radar.
It can also jam communications between the drone and its operator, enabling authorities to take control of and land the drone.
Sussex Police Assistant Chief Constable Steve Barry said less sophisticated options are also available, including shotguns, although blasting drones out of the sky was one of the least effective tactics.
Police are keeping an open mind over the motive, with theories including an environmental protest, but are not treating it as a terrorist incident.
Mr Barry said there is no evidence of involvement of a foreign power, but described the drone activity as "really high-end criminal behaviour".
"This is a really significant criminal offence," he said.
"There are resources here at Gatwick Airport now to mitigate the threat of that and a lot of resources to bring the offender to justice."