The Civil Aviation Authority of Nepal (CAAN) has restricted takeoff and landing weight for all international airlines flying widebodies to Kathmandu’s Tribhuvan International Airport (TIA) to 196 metric tons (432,102 pounds) through September 30. The decision is a result of safety concerns following repeated cracks on the 46-year-old runway.

According to the CAAN, heavier aircraft (up to 299 metric tons/659,175 pounds) have been responsible for cracks and potholes on the runway. Airport officials speaking on condition of anonymity attributed the runway damage to the use of substandard materials and construction techniques, noting that the runway is just three to four inches thick, compared with the industry norm of approximately 10 inches.

Runway problems emerged in 2010, a year after a resurfacing project.

“Surface irregularities may adversely affect the takeoff or landing of an aeroplane by causing excessive bouncing, pitching, vibration or other difficulties,” cautions ICAO’s Aerodrome Design Manual.

The results of an ongoing study on the Kathmandu runway by a Spanish company will determine what repairs are required and could necessitate closing the airport (Nepal’s sole international field) for more than three months.

The restriction comes at the height of Nepal’s tourism season. Air Asia, Korean Air, Thai Airways and Dragon Air already operate widebodies to TIA, and Etihad Airways, Qatar Airways and Turkish Airlines had announced plans to operate widebodies there beginning this month.

“Though we are working on payload reduction to reduce load on the runway, it is not a permanent solution as airlines will incur huge losses if they [have to cut back on] passengers, baggage, cargo and fuel,” said Bharat Kumar Shrestha, chairman of the Airlines Operators Committee Nepal, an association of foreign airline operators.