Financial Times 
July 26, 2011
Two Chinese fighter jets crossed an unofficial dividing line in the Taiwan Strait late last month in pursuit of a U.S. spy aircraft, according to defense sources in Taipei and Beijing.
The incident marked the first time in more than a decade that Chinese military aircraft have entered Taiwan’s side of the 180km-wide strait. According to Taiwan’s defense ministry, two Chinese Su-27 fighter jets briefly crossed the so-called “middle line” on June 29.
Confirmation of the close encounter comes as the U.S. and China are trying to cool tensions in the South China Sea and safeguard a recent improvement in bilateral military relations.
Taipei, whose relations with Beijing have also been on the mend, moved to downplay the incident. “This was not between Taiwan and China, but between China and the U.S.,” said a senior Taiwanese defense official. “The Chinese crossed the line to repel a perceived intrusion by a U.S. reconnaissance aircraft.”