The first Lockheed Martin-[LMT] built F-35 Lightning II for the international program recently rolled out of the factory and is scheduled to be delivered to the United Kingdom next year, the company said recently.

The U.K. Defence Ministry is buying the short-take off and vertical-landing (STOVL) version of the F-35 and is a level one partner in the development program, based on the country’s financial stake. The STOVL variance is the same model the Marine Corps is procuring and is designed to launch and land on smaller aircraft carriers.

The first U.K. multi-role fighter will be known as the BK-1 and is for training and operational tests.

“This first F-35 for the first international program partner is symbolic of the proud partnership we share with the United Kingdom,” said Tom Burbage, Lockheed Martin’s vice president and general manager of the F-35 program.

The F-35 program has embattled major cost overruns and delays. The STOVL variance has been the most troubled version and has been placed on probation by the Pentagon. The Marine Corps says the program is getting back on track and is trying to have probation lifted.

The Defence Ministry said the plane will fly from land and from its new Queen Elizabeth class aircraft carrier.

“This is a major milestone in the JSF program for U.K., and we look forward to starting to operate the first British F-35s next year,” said Group Captain Harv Smyth, the U.K.’s Joint Strike Fighter (JSF) national deputy.

Tier two and three developing partners in the fifth generation fighter program are Italy, Netherlands, Turkey, Canada, Australia, Denmark and Norway. Israel has selected the F- 35A version as its next generation fighter through the U.S. Foreign Military Sales process. Japan and South Korea are also considering the F-35 to recapitalize their fighter fleets, Lockheed Martin said.