Taiwan's air force is no longer scrambling each time Chinese aircraft encroach on its air defense identification zone (ADIZ) but tracks the intruders with ground based missiles instead to help save resources, a senior official said Monday.

Taiwan's air force has repeatedly scrambled to intercept Chinese jets in recent months, and the United States approved in July a possible $620 million upgrade package for Patriot surface-to-air missiles to Taiwan.

Twenty Chinese military aircraft entered Taiwan's ADIZ on Friday, in the largest incursion yet reported by the island's Defense Ministry and marking a dramatic escalation of tension across the Taiwan Strait.