Cleared for takeoff... but not by anybody in the control tower.

City Airport in London has become the first major hub to do away with on-site controllers.

Its old tower is now deserted, replaced by a digital mast bristling with sensors.

Humans are still watching over everything.

But they're at an air traffic control centre 90 miles to the southwest.

They direct planes using video, audio and data feeds.

Lawrie McCurrah is watch manager:

"So, it's definitely different not being at the airport anymore you don't have that smell of jet fuel when you arrive at work, but we've done a lot of work to make it feel as if you're there as much as possible. So the system has ambient microphones on the mast so that we can still hear the aircraft and so you still hear them powering up to depart, you still hear the reverse thrust come in as they land, and it really is very similar to being on site."

City Airport says the new system is more efficient, and will allow it to operate more flights per hour.

Though the smallest of London's airports, it still handled 5 million passengers a year before the global health crisis.

Now managers say big airports around the world are watching to see how well it works.

Alison Fitzgerald is chief operating officer at City:

"Well, as you can imagine it quite often raises an eyebrow, but then when you think about what we've done and the change that we've made, you know, what we're doing is adding to the functionality and the information that the air traffic controllers have."

London's biggest hub - Heathrow - is reported to be considering remote control towers for its future plans.