Next generation combat unmanned aerial vehicles (UCAVs) and long-range missiles will soon replace the United Kingdom’s fighter fleet, a top British military official said this week.

“We are looking toward a technological leap in the second half of the 2020s,” said Gen. Nicholas Houghton, vice chief of the British defense staff. “At that point, we will move away from manned fast jets to UCAVs and missiles.”

Houghton was speaking at a press briefing ahead of an event sponsored by the Center for Strategic and International Studies, a Washington think tank.

The details of when the United Kingdom goes completely unmanned for the deep-strike mission will be determined when London conducts its next strategic defense review in 2015, according to the general.

The United Kingdom had been the Pentagon’s most significant international partner in the F-35 Joint Strike Fighter development effort until earlier this month. London had plans to purchase the short take-off/vertical landing (STOVL) version of the aircraft. However, last week’s release of the 2012 Strategic Defence and Security Review (SDSR) unveiled recommendations for cutting defense spending by eight percent over four years, reducing the number of F-35s to be acquired and dropping the B model is in favor of the carrier variant of the aircraft.

Lockheed Martin [LMT] is building three versions of the F-35 for the Air Force, Navy and Marine Corps, as well as several foreign militaries. The A model, to be flown by the Air Force, takes off and lands conventionally; the Marine Corps’ B model is a STOVL variant; and the C model is to be flown from carriers by Navy fighter pilots.

The B model, which is technologically the most difficult of the three variants to build, has suffered by far the most setbacks in development and testing.

The Royal Air Force plans to fly a fleet of Eurofighter Typhoons and F-35s by 2020. The Typhoon is replacing the F3 Tornadoes, while the GR4 ground attack variant will eventually be replaced by F-35s.

Houghton said a desire for increased payload, range and interoperability with the U.S. and French navies, in addition to concerns about rising costs of the F-35B, led to the decision to move to the C model.

Houghton added that he feels the British military came out of the SDSR “in good shape.” He noted that the coalition government still plans to spend just over two percent annually on defense and that other agencies took much larger financial hits.

He said the review “underscores London’s security partnership with Washington,” while at the same time moving toward a closer military cooperation with France. He said the two allies are the “most militarily capable in Europe,” making a close partnership “sensible.” The general added that the United Kingdom would remain Washington’s “most capable” ally.

Houghton also weighed in on the U.S. Air Force tanker competition, saying that it would be “a good thing” if the Pentagon chooses an Airbus-based KC-X over the Boeing [BA] offering.

“It would make sense. It would be a commercial good idea,” Houghton said. “From the position of the United States, it’s got to answer the operational requirement, but I think it would be a good outcome.”

Houghton said choosing the Airbus plane would also be “an article of mutual faith” for the new bilateral foreign military sales agreements between London and Washington.

The United Kingdom has signed a $16 billion lease deal for 14 modified Airbus A330 aircraft, supplied by parent company European Aeronautic Defence and Space Co., for its own tanking needs. London is also discussing sharing its new fleet with France as part of their defense cooperation agreement.