After Pakistan facilitated the 1972 US-China rapprochement, and especially during the later stages of the Cold War, the US had tacitly encouraged Pakistan to give China access to US technologies in order to improve its budding relationship with Beijing and pressurize erstwhile USSR. In 1975, the US endorsed the UK’s sale of 50 Spey jet engines to the China along with a factory to produce them. In 1982, it approved the sale of AN/ALR-69 radar warning system to Pakistan on the F-16 aircraft despite CIA’s explicit warnings about its proliferation to China. Such technology transfer allowed the US (and Pakistan) to work with China till 1989 to support the mujahideen in Afghanistan.
One of the ‘Tomahawk’ cruise missiles fired in the 1998 US attack on an Al Qaeda camp in Afghanistan crash-landed in Baluchistan – and was transferred by Pakistan to China, who re-engineered it as the air-launched KD-20. Following the May 2011 raid that killed Osama bin Laden, Pakistan reportedly granted China discrete access to the crashed US’ state-of-the-art stealth helicopter.