According to them, two Russian Su-27s carried out an "unsafe and unprofessional" interception of an MQ-9 drone. One of the fighters dumped fuel several times and flew in front of a U.S. UAV "in a reckless and environmentally damaging manner."
As a result of these maneuvers, the Su-27 hit the Reaper propeller and the Americans had to flood their damaged drone in international waters.