The Ministry of Defence put pressure on regulators to delay safety warnings about a new drone it planned to fly over British skies to avoid tipping off protesters, according to official documents obtained by the Guardian.

They reveal how the ministry was embroiled in a behind-the-scenes row with British safety regulators over the US-built drone, which was being flown from North Dakota to a military base in Gloucestershire.

The drone, named “Protector”, will be able to attack targets in many parts of the world with precision missiles and laser-guided bombs. With a wingspan of 24 metres, it can remain airborne for up to 40 hours with a maximum speed of 240mph. It will replace the current generation of drones, known as Reapers, which are not permitted to fly over Britain because of safety issues.

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Normally civilian pilots flying commercial jets, private planes and gliders in British airspace are given 60 days’ notice to stay clear of specific blocks of airspace, known as temporary danger areas, to avoid mid-air crashes.

However, the documents reveal that the MoD wanted regulators to give only six days’ warning to the public. The ministry wanted to prevent protesters organising a demonstration about the drone, according to the documents.

Regulators said that the longer the delay in issuing the warnings over the Protector flight to Gloucestershire, which took place in the summer of 2018 and was the first time a drone had made a transatlantic journey through British civilian airspace, the higher the risk of other planes crashing into the drone.

They complained that they had received “huge” pushback from the MoD to delay as long as possible, despite the danger to gliders holding a competition close to the route that the Protector drone was scheduled to take.

The MoD is spending more than £1.1bn to buy a 16-strong squadron of Protector drones that will be able to fly for twice as long as the Reapers they are replacing. They are scheduled to start operating by 2024 from a Lincolnshire airbase. The MoD is buying the drones from the US arms manufacturer General Atomics and chose to call it Protector in contrast to the previous American model, named Predator.

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General Atomics flew one of the new drones to an airbase in Fairford, Gloucestershire from its test centre in North Dakota in the US in July 2018. The firm displayed the drone at a huge airshow where more than 100,000 spectators viewed hundreds of military aircraft from around the world.

Emails released under the Freedom of Information Act have revealed the row between the MoD and the Civil Aviation Authority, which is responsible for aviation safety in the UK.

A month before the scheduled 11 July flight, a CAA official wrote to a colleague: “General Atomics had wished to issue a press release last week or early this week but the MoD has blocked this due to concerns about the potential for ‘anti [military] drone’ protests hampering the arrival at Fairford if the flight is publicised too early.”

The official said “clearly there is a conflict between the MoD’s concerns” and that the CAA needed to warn others that designated blocks of airspace had to be closed off.

On 19 June, a CAA official wrote there was an MoD worry about anti-drone protesters “hindering this flight or causing a scene”.

Another CAA official said the MoD wanted the warnings publicised on 5 July, when usually they would be issued at least 60 days before specific sections of airspace were closed. “We have significant concerns this is too late,” the official wrote. “The longer we leave it to notify, the higher the risk of airspace infringements.”

One official wrote that “patience is running thin thanks to the MoD”, while another said: “We are running out of time here and the MoD now trying to run this is inducing frustration.”

On 20 June, a CAA official emailed General Atomics to say that gliders were organising a big competition about 10 miles north of the drone’s intended flight path. “We feel this is now a huge push to go public, so the British Gliding Association and other airspace users can plan accordingly to remain clear of the [drone’s] airspace,” the official wrote.

The CAA ended up overruling the MoD and issued a safety warning to the public on 25 June – about two weeks before the drone flew to Fairford over Wales.

Anti-drone protesters said the military’s clandestine pressure on the independent British safety regulator over the flight was extremely worrying.

Chris Cole, founder of the Drone Wars group that campaigns to ban drones, said the CAA would make significant decisions on the safety of the new generation of military drones. “The fact that the MoD has already successfully exerted pressure to get the CAA to bend safety rules in relation to the flight of a Protector is extremely disturbing,” he said.

According to Cole, the 2018 flight was a PR exercise also designedto help convince safety regulators that the Protector drone – unlike the current generation of Reapers – could be flown regularly in Britain’s skies.

Responding to a request for comment, an MoD spokesperson said the ministry “had worked collegiately with the CAA, and multiple other parties to ensure the successful participation” of the drone at the airshow. “This meticulous planning ensured that the flight was completely routine, demonstrating the ability of the crew and aircraft to safely integrate into civilian airspace,” they said.