The choppers had been used during the Balochistan operation and different anti-narcotics operations, according to Pakistani sources.
Reports suggest that U.S. has taken back the choppers after Pakistan failed to secure an agreement to further retain them.
In 2002, the US had provided Pakistan with nine helicopters for manning the Pak-Afghan border to control militant activities. Earlier on October 15, Pakistan had returned four of these helicopters to the US.
According to reliable sources, the remaining aircraft were safely loaded on a transport aircraft in the federal capital on Monday and were expected to reach the US early on Tuesday.
US President Donald Trump had slammed Pakistan for its continued support to terrorist groups and warned Islamabad of consequences if it continues to do so while announcing his Afghan and South Asia policy in August.