Pakistan never donated AKSAI CHIN, because Pakistan never had Aksai Chin to begin with, in fact Ayub Khan saw this coming & made India an offer of a joint defense. Aksai Chin is a freaking 38,000 sq km piece of real state !
Ayub's offer was straight save 38,000 sq km & accede us just 10,000 sq km in the valley & you still get to keep a freaking 28,000 sq km of territory ! Pak @ that time had all the quality weapons from the west, one could ask for, it was a member of seato & cento, stationing a few state of the Art weapons from America & the Mid-East in Aksai Chin especially against China was quite an easy task & he had the assurances for it as well ,but India being the rigid type that it was Refused ! after the debacle that India had suffered, China entered in to Shsakham valley & gave us two choices , which was concede 1,500 sq mi of it, & save 750 sq mi of its total 2,250 sq mi or loose it all, like India with a beating ! or give it to us, respectfully that way @least you get to keep 750 sq mi of it, & in these conditions any sane person would have taken the later, (koi bhi apni zameen kisi ko shokh se nahi deta ,majboori hoti hai apni ,apni ) Aksai Chin was with India, till it lost it to China ,from 1959 to1962 period when, China started claiming that Area & started to encroach it , India reacted to it ,& send its forces on an offensive to drive the PLA out, which was known as the forward policy , & China went ferocious & retaliated with a full fledged invasion of Aksai Chin & Northeast India & successfully captured Aksai Chin & Arunachal Pradesh & parts of Assam
, India went on an panic mode , China cultivated a brilliant strategy of a two pronged successful invasion & announced a unilateral cease fire & a retreat offer from the north east India only, with China getting Aksai Chin & a few small parts of utarkhand & himachal ,it was a loose one or both situation, with India choosing to loose one (Aksai Chin)