Two Chinese fighter jets conducted an "unprofessional" intercept of a U.S. aircraft in international airspace over the East China Sea on Wednesday, according to the U.S. Air Force.
The American aircraft was conducting a routine mission in accordance with international law when the two Chinese SU-30 jets made the move, Pacific Air Forces spokeswoman Lt. Col. Lori Hodge told The Associated Press.
One of the SU-30s flew upside down directly above the U.S. plane and both of the Chinese jets came within 150 feet of it, CNN reports.
Hodge said the crew aboard the American plane described the move as unprofessional due to its speeds and proximity.
The U.S. aircraft, a WC-135 Constant Phoenix, is used by the Air Force to detect atmospheric traces of nuclear explosions. The WC-135 have been used in the past to collect evidence of North Korean nuclear tests, according to CNN.
"In 2013, China declared an air defense identification zone over much of the East China Sea and it requires foreign aircraft in the area to follow its orders," NPR's Anthony Kuhn reports. "The U.S. refuses to recognize the zone, and it is unclear whether the incident took place in it."
Hodge told the AP that "U.S. military aircraft routinely transit international airspace throughout the Pacific, including the East China Sea. This flight was no exception."
The incident comes at a time when China and the Trump administration have apparently agreed to cooperate on the North Korean nuclear issue.
Wednesday's encounter isn't the first close call this year. In February, CNN reported on an "unsafe" encounter over the South China Sea when a U.S. Navy P-3 Orion reportedly had to change course to avoid colliding with a Chinese surveillance plane — and that a U.S. official said the aircraft came within 1,000 feet of each other.
As for Wednesday's intercept, the AP quoted Hodge as saying that it's "being addressed with China through appropriate diplomatic and military channels." She added that discussing it privately with China, "will allow us to continue building confidence with our Chinese counterparts on expected maneuvering to avoid mishaps."