Two U.S. Navy pilots were shot down Sunday over the Red Sea in an apparent “friendly fire” incident, the U.S military said, marking the most serious incident to threaten troops in over a year of America targeting Yemen’s Houthi rebels.

Both pilots were recovered alive after ejecting from their stricken aircraft, with one suffering minor injuries. But the shootdown underlines just how dangerous the Red Sea corridor has become over the ongoing attacks on shipping by the Iranian-backed Houthis despite U.S. and European military coalitions patrolling the area.

The U.S. military had conducted airstrikes targeting Yemen’s Houthi rebels at the time, though the U.S. military’s Central Command did not elaborate on what their mission was and did not immediately respond to questions from The Associated Press.