A US Air Force refueling aircraft crashed in western Iraq during a mission supporting military operations against Iran, killing all six crew members on board, according to US Central Command.

The aircraft, a KC-135 Stratotanker, went down Thursday in what US officials described as a non-hostile incident in “friendly airspace,” prompting an investigation into the cause of the crash.

Military officials said the tanker was involved in an incident with another KC-135 aircraft while conducting aerial refueling operations as part of Operation Epic Fury, the US offensive linked to the ongoing conflict with Iran. The second aircraft managed to land safely, authorities said.

US Central Command said the crash was not caused by hostile fire or friendly fire, and the circumstances surrounding the accident remain under investigation.

The tanker was carrying six crew members, all of whom were confirmed dead. Their identities will be released after their families are notified, officials said.

The KC-135, one of the US military’s primary aerial refueling aircraft, has been in service for decades and plays a crucial role in extending the range and endurance of combat aircraft during long-distance operations.

The incident occurred amid heightened military tensions in the Middle East linked to the ongoing US-Iran conflict, where thousands of American troops are deployed across the region.

Meanwhile, an Iran-aligned armed group in Iraq claimed responsibility for bringing down the aircraft, though US officials denied the claim and said there was no indication the crash was caused by enemy action.