PARIS (AP) — Skies over the Paris region will be closed for six hours as part of the massive security operation for the July 26 opening ceremony of the Olympic Games, the Paris airports operator said Wednesday.

Augustin de Romanet, chairman of Aéroports de Paris, said airlines are being warned in advance about the closure and told they will have to fly around the restricted airspace.

“For six hours, there won’t be any aircraft over the Paris region,” he said on France Info radio.

The no-fly zone will extend for a radius of 150 kilometers (93 miles) around Paris, the civil aviation authority and Interior Minister Gerald Darmanin have said.

The unprecedented waterborne ceremony on the River Seine running through the French capital is the stiffest single security challenge for Paris Games organizers, with crowds of more than 320,000 people expected to line the waterway.

At least one French military AWACS surveillance aircraft will police the skies during the Olympics, using its powerful radar to watch for any potential airborne threats, the French AWACS squadron’s commander previously told The Associated Press. Other military aircraft can be scrambled to intercept any non-authorized flights that enter restricted Olympic airspace.

Separately, de Romanet said there’s still a “very, very high” probability that small electric-powered airborne taxis will be trialled with passengers over Paris during the July 26-Aug. 11 Games, which he said would be a world first.

But European air-certification authorities might initially only allow the taxis to fly passengers on an experimental basis, not commercially, he added.

“We have high hopes that we will be able to carry passengers experimentally which will pave the way, over Paris, for the first flight in the world of an electrical vertical take-off aircraft,” he said.

Multiple companies are developing electrically powered aircraft that take off and land vertically. Some have already flown demonstration flights, in a race to turn their promises of environmentally friendly air transport into a commercially viable reality.

De Romanet insisted that the aircraft are safe, saying: “I am ready to climb aboard.”

Critics worry that taxis zipping through the airs of Paris will be a noisy and potentially dangerous nuisance and affordable only by the wealthy. The Socialist mayor of Paris, Anne Hidalgo, is among opponents of proposals to trial them on a few Paris-region routes during the Games.

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