The search is underway for a second crew member of a downed U.S. fighter jet in Iran.

One pilot has been rescued, according to the U.S. Air Force.

The second is missing.

The plane, an F-15E Strike Eagle, was reportedly downed by the Iranian Revolutionary Guard Corps over central Iran, specifically in the mountainous Kohgiluyeh and Boyer-Ahmad province.

It is the first U.S. fighter plane lost in combat operations in Iran since the beginning of Operation: Epic Fury five weeks ago.

President Donald J. Trump has been briefed on the fighter jet’s downing and the rescue operations that are underway.