State carrier Lao Airlines has a near-monopoly on domestic flights, a dodgy safety history in the past, but a good safety record now. The fairly comprehensive network is by far the fastest (and, relatively speaking, the safest) way of reaching many parts of the country. As of 2014, the popular Vientiane-Luang Prabang route costs about USD200 (one-way), but covers in 40 minutes what would take you at least ten to twelve hours by bus. Flights to more remote destinations, though, are flown on the Xian MA60, a Chinese knockoff of the Soviet An-24, and are frequently cancelled without warning if the weather is bad or not enough passengers show up.
Lao Airlines also flies 14-passenger Cessnas from Vientiane to Phongsali, Sam Neua and Sainyabuli (Xayabouly) several times a week. These airfields are all rudimentary and flights are cancelled at the drop of a hat if weather is less than perfect.