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

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