This was at most about 1100nmi from Gaya and the plane has a range of 1500-1600nmi (with reserves, I believe). If it was just range reduction due to headwinds I'd think they'd have known well beforehand that they weren't getting to Tashkent. I wonder if it would have been legally or practically possible to refuel in Islamabad, since their fuel situation ought to have been apparent by that point.