VietJetAir is usually the cheapest airline on domestic routes within Vietnam, beating both Jetstar and national Vietnam Airlines on price. Connections between major cities are very frequent with several flights within an hour. The cheapest one-way tickets are usually just under 29 eur.
The company flies to virtually every civilian airport in Vietnam, with international routes mainly to Thailand, Cambodia, Singapore, China and Taiwan.
VietJetAir's pricing is a bit odd. The cheapest tickets on promo fares tend to be available 4-6 months in advance, with the most expensive prices departing between 1 and 3 months in advance. Conversely, last minute prices can drop slightly, albeit to the values of the lowest promo fare. However, the differences are not large (maximum 11 eur - 18 eur ).
Be aware that the initial price quoted is not the final price, and once the flight is selected, fees will still be added, usually around 13 to 20 usd.