The Wrong Side of the Sky — Gavin Lyall

A chance encounter in an Athens bar with war-time flying buddy sets Jack Clay on the trail of the Nawab of Tungabhadra's missing fortune, hi-jacked out of India years before at the time of partition. Maybe there would be nothing much in it for him at the end of the day, but it sure beat the hell out of growing old and obsolete together with the dilapidated Dakota in which he flew everything anywhere on a wing and a prayer and a bottle of Scotch. Clay badly needed out. This might be his last chance. But there were others whose needs were as great as Clay's. Men--and women--who were prepared to lie and cheat, murder and maim, to get to the diamonds first…