DUBAI, United Arab Emirates — The fate of the MQ-9 Reaper has once again entered public debate after senior U.S. defense officials confirmed Houthi militants had downed one of the drones over international waters off the coast of Yemen on Nov. 8. In recent years, experts have questioned the sustainability of flying such expensive aircraft in contested environments , where less costly countermeasures are able to target them. For example, in 2021, the Air Force sought to curtail procurement of