Paro International Airport (Dzongkha: སྤ་རོ་གནམ་ཐང༌།, romanized: program thang) (IATA: PBH, ICAO: VQPR) is the sole international airport of the four airports in Bhutan. It is 6 km (3.7 mi; 3.2 nmi) from Paro in a deep valley on the bank of the river Paro Chhu. With surrounding peaks as high as 5,500 m (18,000 ft.), it is considered one of the world's most challenging airports, and only eight pilots are certified to land at the airport. Flights to and from Paro are allowed under visual meteorological conditions only and are restricted to daylight hours from sunrise to sunset. Paro airport was the only airport in Bhutan until 2011.