Taiwan activated fighter jets to potentially engage in combat Thursday after 39 Chinese aircraft trespassed into its claimed air defense zone, Taiwan’s defense ministry said.

Elements of China’s air force have entered Taiwan’s air defense identification zone, or ADIZ, nearly every day since House Speaker Nancy Pelosi visited the island in March, an event China condemned as a provocation, the Taiwan Ministry of Defense’s website tracker shows. In response to Thursday’s incursion into airspace on Taiwan’s southeastern waters, Taiwan tasked combat aircraft, or scrambled them, to warn away China’s incursion, the ministry said.

Thursday’s incursion involved four H-6 bombers, 21 fighters jets and support aircraft, according to the island’s defense ministry. Taiwan also identified three Chinese People’s Liberation Army Navy (PLAN) warships patrolling the waters near the island.

The incursion is the largest since Nov. 7, when 63 aircraft flew near Taiwan, with 31 crossing the unofficial line of demarcation between China and Taiwan in the Taiwan strait. The island has repeatedly complained over the past two years of sustained Chinese violations of its ADIZ, which it sees as an attempt to intimidate the island’s leaders.

Separately, Taiwan said the National Chung-Shan Institute of Science and Technology, the research division of Taiwan’s ministry of defense, planned to conduct a missile firing drill off the southeastern coast, according to Reuters.

Taiwan’s defense ministry threatened in August that it would strike Chinese armed forces if they come within 12 nautical miles of the Taiwanese air and sea territory. China’s “high intensity” patrols signaling China’s aims to bring the intermediary waters under full Chinese control would constitute the main sources of instability in the region, the ministry said at a press conference Wednesday.

“There is only one China in the world and Taiwan is an inalienable part of China’s territory,” Chinese Foreign Ministry spokesperson Mao Ning said on Tuesday.

China appears positioned to attack Taiwan in the near future, Secretary of State Antony Blinken said in October, noting that Beijing has accelerated its timeline and redoubled commitments to “reunification.”