A Russian military plane collided with a U.S. drone in international airspace over the Black Sea on Tuesday, prompting U.S. forces to land the unmanned aircraft in international waters.

U.S. European Command confirmed that a Russian Su-27 aircraft struck the propeller of a U.S. MQ-9 drone, which was on a routine mission in international airspace when two Russian jets attempted to intercept it.

“Several times before the collision, the Su-27s dumped fuel on and flew in front of the MQ-9 in a reckless, environmentally unsound and unprofessional manner. This incident demonstrates a lack of competence in addition to being unsafe and unprofessional,” a spokesman for the U.S. European Command said in a statement.

The Russian jets’ recklessness almost caused one of the fighter jets to crash, the statement added.