After six years of operations, Detachment H ended the U-2 overflight of Chinese territory in March 1968, as recorded in CIA’s OSA Chronology. The last overflight mission was coded C058C and flown by Andy Fan (范鴻棣):
The track below shows that the mission covered Yunan (雲南) Province of Southern China. Since the mission lasted only 4+40 hours, the flight could not have been launched from Taiwan. It was very likely to have originated from Thailand.
After C058C, Detachment H flew another ELINT mission in May and then the US government ordered it to stand down, as shown in the following July 1968 document:
The stand-down order was finally lifted in October 1968. But all flights since then were not allowed to enter Chinese mainland and had to keep a minimum distance of 20 nautical miles.
Later we shall see more and more stand-down orders came from the US for political reasons.