(ASSOCIATED PRESS) — All six crew members of a KC-135 refueling aircraft supporting operations against Iran are dead, the U.S. military said Friday, after their plane crashed in western Iraq. The U.S. Central Command, which oversees the Middle East, said the crash followed an unspecified incident involving two aircraft in “friendly airspace,” and that the other plane landed safely. The crash brings the U.S. death toll in Operation Epic Fury to at least 13 service members, seven of whom were killed in combat. About 140 U.S. service members have been injured, including eight severely, the Pentagon said earlier this week. Here’s what is known so far about the tanker, which is the fourth publicly acknowledged U.S. aircraft to crash during the war against Iran: The U.S. Central Command said all six crew members on board the crashed KC-135 have been confirmed dead. It said the circumstances of the crash are under investigation but that the loss of the aircraft was “not due to hostile or friendly fire.” A U.S. official, who also spoke on condition of anonymity to discuss the developing situation, said the other plane involved was also a KC-135. Yechiel Leiter, the Israeli ambassador to the U.S., wrote on X that the other plane landed safely in Israel. Yang said it would be rare for a refueling tanker to be downed by enemy fire because such operations are usually conducted in the rear of combat zones. The crash came after three U.S. F-15E fighter jets were mistakenly downed last week by friendly Kuwaiti fire.