Gatwick is the UK's second busiest airport (Picture: N Chadwick).
The runway at Gatwick airport has reopened and the first plane to arrive since Wednesday evening has landed at the airport's North Terminal.
Gatwick says a limited number of planes should leave and arrive in the next few hours, after a drone halted all flights yesterday.
The British military were called in yesterday and deployed "specialist equipment" to assist police.
The Defence Secretary said personnel were deployed after a request from Sussex Police for support.
Gatwick chief operating officer Chris Woodroofe said the airport has scheduled almost 700 departures for today.
Mr Woodroofe, speaking to BBC Radio 4's Today programme, said: "Our advice to our passengers is to check with their airline on each of those flights that they're intending to get, to establish whether it's one of the flights that's being operated or one of the flights that's being cancelled, before they come to the airport.
"I'd just like to apologise to all of those affected over the last 36 hours - 120,000 passengers who were due to fly to their destinations or arrive into Gatwick who have not travelled."
Mr Woodroofe was pressed on why the airport had decided to reschedule flights while the drone had not been found, he said:
"We have been working overnight with the police, with a number Government agencies and with the military to put in place additional mitigating measures which have enabled me to reopen our airport."
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."
How could the drone be dealt with?
A high-frequency radar could be used to interfere with the control of the drone, which would then have to go into a safe mode and land.
Another system uses an air pressured shoulder-launched net and which entangles the drone forcing it to crash.
In theory, if the drone was low enough you could just use shotguns because of the low range of these weapons but that would probably be unacceptable to the authorities.
If projectile type devices are used then they need to be low velocity to remain within the airport boundary.
If the drone subsequently crashed on the runway the clean up will involve far less disruption than the airport being closed for an extended period.
A former Royal Logistic officer told Forces News the drones could have been brought down safely with existing technologies.
"Drones rely on a direct radio link with their operator," said Richard Gill.
"By breaking that radio link you nullify the drone's abilities.
"Most drones, 90% plus of drones, once that radio link's broken will enter a 'return-to-home' failsafe mode where they just fly out of the area and go back to the operator.
"When it's flying back to its operator you can then follow that drone and figure out where the operator is."
Should The Military Be Called In?
We asked a military analyst...
Air defence from the ground is the remit of the Royal Artillery who have weapons such as the High-Velocity Missile system which can be used against drones.
However, these weapons can be dangerous and are designed for use on the battlefield against Unmanned Aerial Systems (UAS)
Likewise, you cannot simply fire a sniper rifle at it because the bullet could travel several miles and would be unsafe in an urban environment.
There are already systems that can be used by trained civilian airport staff to counter the drone threat.
One system that has been developed by UK companies is the Anti-UAV Defence System (AUDS).
This has been tested by the US federal Aviation Authority FAA and uses radar to locate the drone, then tracks it using a thermal camera.