DUBAI, United Arab Emirates (AP) — 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.

Two US Navy pilots ejected safely after their fighter jet was shot down over the Red Sea on Saturday in an apparent friendly fire incident, US Central Command said in a statement.

The guided missile cruiser USS Gettysburg, part of a carrier strike group in the region, mistakenly fired on the jet, U.S. Central Command said.