Similair to 'airclues' - but I flew 707's for BOAC in the late '60's early 70's - initially we flew almost due east from BKK across S.Vietnam and later up over Da Nang . Usually I think we flew across at FL290 or even 280 and apart from the view of the countryside looking like the UK on Bonfire night, never recall seeing anything military - and we were looking!