Two U.S. F-35 fighter jets arrived on Tuesday in NATO member Estonia to take part in the military alliance’s drills as the aircraft saw their first operational deployment in continental Europe.

The planes with stealth technology to avoid detection by radar landed at the Amari air base from a base in Britain.

Air Marshal Stuart Evans of NATO’s Allied Air Command said the F-35s will be “the fundamentals” in the military alliance’s capabilities to defend the air sovereignty of its members.

“If you look at the challenges to our security environment, our ability to dominate the air environment, this aircraft is one of the fundamentals as we go forward into the future to face any potential security challenges,” Evans told The Associated Press.

The F-35 deployed to Europe are permanently stationed at an U.S. air base in Utah and are part of the Pentagon’s most expensive weapons program, estimated to cost around $400 billion.

One of the U.S. Air Force pilots of the F-35 planes was Lt. Col. George Watkins, who was impressed with aircraft’s performance.

“The F-35s are amazing,” said Watkins, who has flown the plane for around two years now. “It takes our capability to a whole new level of technology. Just the stealth capability alone is really amazing for the pilot because it increases our survivability and allows us to go where other planes can’t go.”

He said the plane conducted one airborne refueling session from the accompanying KC-35 tanker plane during the three-hour flight en route from Lakenheath in eastern England to the Baltic country.

Earlier this month, the U.S. Air Force deployed a fleet of F-35s, its newest and most powerful fighters, to Britain to reassure U.S. allies in the face of Russian aggression.

U.S.A.F. said the F-35s will remain “a period of time” in Estonia to conduct air drills with NATO aircraft in the region “in a realistic training environment.”

(AP)