Nguyen Cong Hoan, deputy director of Ha Noi Red Tours, said flights from Ha Noi to Hue and Ha Noi to Da Nang were not available at low prices.
The company at times has had to buy tickets at higher prices or shifted to tours by train for the Ha Noi - Da Nang tour.
Although Vietnam Airlines (VNA) committed to offer special discounts until September under the promotion, only some routes apply.
Prices for flights between Ha Noi and Nha Trang from June to August are not included.
Tran The Dung, deputy director of HCM City-based The He Tre tourist company, said tickets for southern companies were especially hard to buy because of the high demand.
VNA said it had increased the capacity of flights, but demand for domestic, rather than international, flights had led to overbooked local flights.
Dung said tour operators should be flexible in booking tickets for their customers, and if tickets for day flights were sold out, tour operators should ask travellers to fly at night.
The 30 companies that joined the Impressive Vietnam promotion have cut fares between 30 and 50 per cent for domestic tours.
(Source: VietNamNet/SGT, http://english.vietnamnet.vn/travel/2009/07/856674/)
