RAF Fairford, U.K. – The F-35 will not make its international debut at the Royal International Air Tattoo (RIAT), the air show’s organizers have announced.

RIAT officials say their decision, announced July 10, was made in conjunction with Lockheed Martin as well as the U.S. and U.K. defense ministries. It means that the aircraft will not fly on any of the show days, July 11-13.

Four aircraft – three U.S. Marine Corps F-35Bs and one U.K. F-35B – were set to debut at RIAT. All of them are still in the U.S.

The aircraft have been unable to make their trans-Atlantic crossing because of the grounding of the F-35 fleet announced by the Pentagon on July 3 following an engine fire on the runway at Eglin AFB, Florida, on June 23.

An appearance at the Farnborough air show has not been ruled out, but it is increasingly in jeopardy. A planned July 11 announcement by the U.K. secretary of state for defense, Philip Hammond, at the Air Tattoo has also been canceled because the aircraft will not be present.

The show made its decision as Lt. Gen. Christopher Bogdan, head of the F-35 Joint Program Office, was briefing journalists at Fairford. Despite the announcement, Bogdan said he was still hopeful of getting the aircraft to the U.K.

"As of this moment, the airworthiness authorities need more evidence and we are providing that," Bogdan said. "They are working day and night to try and work out when it will be safe to get back in the air. The U.S. and U.K. are perched at Pax River, and they will sit there until we exhaust the last window of opportunity [to make the trip].

"I can assure you the whole of the enterprise is working to bring this to a safe conclusion."

The groundings were prompted by a fire that broke out on an F-35A preparing for takeoff from Eglin. Initially, commanders at each F-35 main operating base ordered a safety hold, but this was overridden by a Pentagon directive on July 3 that grounded the 100-strong fleet of aircraft.

"It’s not unusual for there to be delays in the development program of any new military aircraft, and the Air Tattoo has been working closely with teams from Lockheed Martin, the U.S. Marine Corps, Department of Defense and MoD [U.K. defense ministry] to ensure the aircraft touched down at RAF Fairford for the Air Tattoo," said the Air Tattoo’s CEO, Tim Prince. "Unfortunately we’ve simply run out of time."

The U.K. defense ministry said the safety of pilots and aircraft had to be the top priority.

"It is disappointing that the Lightning II has not arrived in the U.K. in time for the Air Tattoo, but we fully support the decision not to grant clearance for the aircraft to make their first trans-Atlantic flight to the U.K. until the technical investigations following an engine failure are complete," a spokesman said.