Bangkok is one of Asia's most important air transport hubs. In 2005, more than ninety airlines served Don Mueang International Airport (IATA: DMK; ICAO: VTBD). It was the 18th busiest airport in the world, second busiest in Asia by passenger volume, 15th busiest in the world and fourth busiest in Asia in international passenger volume. Don Mueang consistently ranked 19th in the world in cargo traffic, and seventh in the Asia-Pacific region. Don Mueang is considered to be one of the world's oldest international airports, its opening in March 1914 making it almost twenty years older than London Heathrow. It has three terminals and is located about 30 km (19 mi) north from the heart of Bangkok.

On 28 September 2006, Suvarnabhumi Airport (IATA: BKK; ICAO: VTBS), became Bangkok's official international airport, replacing Don Mueang. Pronounced Suwannaphum (RTGS), or loosely Su-wan-na-poom, the airport is located southeast of the city center in Bang Phli district, Samut Prakan Province. The progress of Suvarnabhumi Airport dates back to the early 1970s when a large plot of land 8,000 acres (3,237 ha) (32 km²) was bought. A student uprising in October of the same year prevented further progress with the development when the military government of Thanom Kittikachorn was subsequently overthrown. After several military coups and the Asian financial crisis of 1997, construction finally began in 2002, after five years of clearing the site. The first flights landed in September 2006, shortly after another military coup. Its two parallel runways are connected by the five concourses of the main terminal building. The airport features a 132.2-metre (434 ft)-tall control tower, the tallest in Asia and one meter (3.2 ft) taller than Kuala Lumpur International Airport control tower. It is the tallest stand alone purpose built control tower in the world.[21] Airports of Thailand Plc. (AoT) have announced another terminal to accommodate a further fifteen million passengers. This will be part of Phase 2 of the airport, which is expected to begin construction in three to five years. The main airline of Suvarnabhumi is Thai Airways International.

Much of the construction of Suvarnabhumi Airport took place during the premiership of Thaksin Shinawatra, who took personal responsibility for its timely completion. Despite a "ceremonial" opening on the planned date, construction was over a year late. Continuing controversy surrounds the quality of planning and construction; accusations include cracks in the runway, overheated buildings, a severe shortage of toilet facilities and lengthy passenger walks to departure gates. The fact that the airport is already overcrowded and near its maximum capacity less than a year after opening is another concern.

Don Mueang remains in use as a base of the Royal Thai Air Force. Most of the low-cost airlines now use the airport for domestic flights, in an effort to ease congestion at Suvarnabhumi, until the next terminal is opened.