FAIRFORD, England —The British public got its first taste of the F-35B short takeoff/vertical landing (STOVL) aircraft purchased for the Royal Air Force (RAF) and Royal Navy at an air show Friday, and it's just possible they also got a glimpse of the next combat jet in line for purchase.

Five F-35s turned up to make their UK debut in the flying display at the Royal International Air Tattoo (RIAT) in Fairford, England, which will last through July 10, before part of the fleet departs for the Farnborough air show, which begins Monday.

Two of the aircraft were the F-35B STOVL variant, already being delivered to the British.

The other three were US Air Force (USAF) F-35As, the conventional takeoff and landing variant purchased by most Lightening II customers to date.

British F-35 officials at the show confirmed there is interest in the conventional takeoff version and that the issue could start to be addressed as soon as the next strategic defence and security review (SDSR), currently scheduled for 2020.

"What we will do as we go forward into the next SDSR is look at the force mix," said Air Commodore Linc Taylor, the Royal Air Force officer responsible for delivery of the British F-35 program.

"There is an absolute benefit to maximizing combat air power with interoperability with Typhoon and the capability from the [aircraft] carrier. We will look at all of those options as we go forward into the next SDSR," Taylor said to reporters at RIAT.

Britain's combat air fleet will be based around the Eurofighter Typhoon and F-35B once the RAF's Tornado strike jet is pensioned off in 2019.

Taylor said the F-35A could bring something to the force mix the other jets couldn't match.

"The F-35A offers you a greater range and greater payload. There may be space for an 'A' variant so we will look at 'A' and 'B's in the future, but not the 'C's," Taylor said. "The F-35 and Typhoon have complimentary qualities but the Typhoon is not low-observable, it can't get to where the F-35 can get to."

The British have looked at a conventional takeoff and landing version of the F-35 before.

At one point in the program the British changed their minds about buying the F-35B and were set to adapt their two aircraft carriers to fly the conventional, naval F-35C variant before the cost of fitting an electromagnetic aircraft launch system made the switch prohibitive.

The decision to switch to the "C" variant was welcomed by senior RAF officers at the time who saw the range and payload of the "B" as a handicap for land-based forces' ability to launch long-range strike.

F-35 Takes Off From RAF Fairford

An F-35B takes off from RAF Fairford, England, and flies to Farnborough to have its flight envelope validated and approved by the UK government. Once cleared, the aircraft can conduct demonstrations at Farnborough International Airshow.

The F-35A has been on the RAF's wish list for a long while, according to Doug Barrier, the senior air analyst at the London-based think tank International Institute for Strategic Studies.

"There has been a long-standing interest on the part of the RAF in the F-35A to meet some of the roles now addressed by Tornado GR4. Greater range and payload performance than the 'B' model, and commonality with the USAF, are likely part of the draw," he said.

"The ground-attack role post the Tornado GR4's retirement could eventually be divided between the Typhoon — equipped with the Storm Shadow long-range land-attack cruise missile and other weapons — and the F-35A, with the latter offering the ability to penetrate airspace defended by high-end threat systems, using medium air-to-surface weapons such as the MBDA SPEAR 3 now in development," Barrie said.

While British interest in a possible F-35A purchase increases, progress in building up its fleet of "B" aircraft is gathering momentum with the delivery the fifth aircraft of eight ordered so far.

Work is progressing for the RAF to declare initial operating capability in 2018, with the Navy planning the first operational deployment of the 70,000-ton Queen Elizabeth-class carrier in 2021.

The British are buying their F-35s in small batches, and although the government committed to buying their full quota of 138 jets in the 2015 SDSR, they are vague on the timing, saying only that the purchase will be completed by the end of the aircraft production program — which could be 20 or more years away.