McAlister's Allegiance — Richard Marman

The 4th book in the McAlister Line: After recovering from injuries suffered at Dien Bien Phu, Danny is straight back into action in Saigon via Taipei.

The 17th Parallel has just been created with the communists to the North. But South Vietnam is awash spies and agents from the CIA, MI6 and other secret service types from the West, but especially Russian, Chinese and with North Vietnamese infiltrators, all vying to fill the, soon to be, power vacuum currently being created by the French who are starting to pull out of Indochina.

Still flying for CAT airlines, commonly referred to as the most shot-at airline in the world, Monty and Angela join him as they plunge headlong into another non-stop, breathtaking odyssey which spreads across five continents, landing in one desperate scrape after another.
Finally all three make heart-breaking decisions which ultimately define their true allegiance.