Vietnam ground combat operations in 1965, and at their peak they numbered more than 500,000. The US also engaged in a sustained aerial bombing campaign. Meanwhile, China and the Soviet Union provided North Vietnam with significant material aid and 15,000 combat advisers. Communist forces supplying the Việt Cộng carried supplies along the Hồ Chí Minh trail, which passed through the Kingdom of Laos. The communists attacked South Vietnamese targets during the 1968 Tết Offensive. Although the campaign failed militarily, it shocked the American establishment, and turned US public opinion against the war. During the offensive, communist troops massacred over 3,000 civilians
Air transport in Vietnam and commercialization of air transportation. The aviation sector expanded greatly during its formative years, expanding from a few aircraft in what was then North Vietnam to eventually include a fleet of over 50 aircraft (including both Soviet- and US-made) in a unified Vietnam after 1976. Infrastructure was improved during this time, as airports country-wide were equipped with better facilities and materials for flight management and operations. CAAV grew to serve around 250,000 passengers a year, both domestically and on international routes to China, Laos, Cambodia and Thailand. On 9 December 2004, United Airlines made history when its Boeing 747-400 landed