TAIPEI (Taiwan News) — A P-3C anti-submarine aircraft recently spotted in the company of two U.S. military planes over the Bashi Channel was probably Taiwanese, former Pentagon official Drew Thompson tweeted Friday (June 26).

Thompson once managed bilateral relations between the U.S. Department of Defense and China, Taiwan, and Mongolia. His remarks followed several days of appearances by Chinese warplanes off Taiwan’s southwest coast and by U.S. military aircraft in the skies between the island and the Philippines.

In a series of tweets, the former official, who now teaches in Singapore, remarked the P-3C spotted by Beijing University’s “South China Sea Probing Initiative” Twitter feed on June 24 was likely Taiwanese. It was flying in the same area as two U.S. Navy P-8 Poseidon aircraft and a U.S. Air Force RC-135W Rivet Joint reconnaissance plane, the Liberty Times reported.

Thompson suggested the aircraft had been tracking and observing a Chinese submarine, adding the Taiwanese must have faced a “steep learning curve” to use the P-3C — not just for maritime surveillance but for anti-submarine tasks as well.

However, he wrote the presence of the Taiwanese and U.S. aircraft in the same area at the same time did not necessarily signal close cooperation between the two countries. “Taiwan saw the U.S. P-8s circling, figured out what was going on, and sent their P-3C to join in the fun,” Thompson tweeted.

In Taipei, the Liberty Times quoted the Air Force as saying it would not comment on speculation.