Jordanian fighter pilots trained closely with their Israeli counterparts at a US-hosted air force exercise this summer, an American official said, in a rare acknowledgment of intimate military cooperation between the Jewish state and its Arab neighbor to the east.

The US official’s comments, reported by Reuters on Tuesday, came as Israel’s Defense Minister Moshe Ya’alon more vaguely confirmed the cooperation. Ya’alon said in a speech Tuesday that Israeli pilots trained with unspecified Arab pilots in the course of July’s “Red Flag,” the latest in a series of joint combat training exercises frequently hosted by the US in Alaska.

Egypt is known to have participated in previous “Red Flag” exercises; Jordan is not.

Get The Times of Israel's Daily Edition by email and never miss our top stories Free Sign Up

“There were Arab pilots there too, and pilots from the various branches of the United States military and other countries,” Ya’alon said Tuesday.

The unnamed US official quoted by Reuters elaborated that Jordanian warplanes flew out with Israel’s jets in the course of the drill, and even refueled from an Israeli tanker over the Atlantic Ocean.

Israel and Jordan signed a peace treaty in 1994, and quietly maintain intimate security and economic relations. But they are not known to have ever acknowledged conducting joint air force training.

While the peace treaty is not popular among ordinary Jordanians, and is routinely criticized during flareups in the Israeli-Palestinian conflict, Israel and Jordan share many regional concerns, including over Iran’s nuclear ambitions and the threat posed by Islamic State.

The disclosure of Israeli-Jordanian air force cooperation came three days after another rare instance of publicly acknowledged cooperation between the Israeli military and an Arab neighbor: Israel on Saturday assisted Egyptian and Russian authorities in the aftermath of the deadly crash of a Russian passenger jet with 224 people on board in the Sinai Peninsula.

IDF spokesperson Peter Lerner said the army coordinated with Russia and Egypt and provided “aerial surveillance in the efforts to locate the Russian airplane that lost contact over the Sinai Peninsula.”

Egypt and Israel signed a peace treaty in 1979.

For the past two weeks, the Israeli Air Force has been hosting the country’s largest ever international air exercise, drilling against a fictional enemy state.

The “Blue Flag” exercise, a followup to “Red Flag” which was due to end on Tuesday, involves the Israeli Air Force, the United States Air Force, Greece’s Hellenic Air Force and the Polish Air Force, the captain in charge of all IAF exercises told The Times of Israel last week. A number of other countries, including Germany, also sent pilots and officers to observe the exercise but did not take part.

“Asked whether Jordan… was among the Blue Flag participants, Israeli military spokesmen declined to comment,” Reuters reported Tuesday. “Jordanian officials also declined comment on both drills,” it said.