Two Chinese fighter jets intercepted an American plane over the East China Sea on Wednesday, according to a Thursday NBC report.

The U.S. aircraft, a WC-135 Constant Phoenix, is commonly referred to a “sniffer” because it detects signs of nuclear activity in the atmosphere by “sniffing.”

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While on a routine mission, two Sukhoi Su-30 fighter planes intercepted the U.S. sniffer as it flew over the East China Sea. The American plane was flying within international airspace and thus in accordance with international law, two U.S. military officials told the news site. They called the actions by the Chinese jets “unprofessional.”

It is unclear whether officials consider the confrontation unsafe.

Officials told NBC that China’s actions are being addressed through "appropriate diplomatic channels."