US officials have claimed that on May 17, 2017, two Chinese Sukhoi Su-30 jets conducted an "unprofessional" intercept of a US WC-135 Constant Phoenix,. They said one of the Chinese jets came as close as 150ft (45m) to the US WC-135 plane and flew upside down above it. US Air Force spokesman Lt Col Lori Hodge said the intercept which took place on Wednesday, was deemed unprofessional "due to the manoeuvres by the Chinese pilot, as well as the speeds and proximity of both aircraft." He said the issue was "being addressed with China through appropriate diplomatic and military channels", and a military investigation was under way. China has not commented on the incident. The aircraft was on a mission in international waters to collect airborne material from nuclear explosions.