Air Vietnam's Caravelle in 1967 - Photo from Pinterest

A Sud Aviation Caravelle was used for Air Vietnam's overseas flights in 1967. By 1973 the airline's international flights were flown on Boeing 707 and 727 aircraft while an old Douglas DC-4 flew the Saigon to Vientiane route. 

Domestic flights were on Douglas DC-3s and other aircraft. One trip I made from Phan Thiet to Saigon was on a single engine Cessna. The Air Viet Nam flight was over ticketed. Anxious passengers elbowed their way aboard to get one of the few available seats.The most aggressive person got to sit next to the pilot.