Airlines, airports and insurers across Asia are bracing for the prospect of unusually high damage as the region's tropical storm season begins, and hundreds of aircraft grounded by the coronavirus pandemic can't be moved easily.

Working staff from Japan's Kansai International Airport arrange luggage for passengers on February 27, 2016. Many Chinese passengers brought empty suitcases to take Japanese products back to China. Photo: VCG

Major airports in storm-vulnerable regions such as Japan, the Philippines, Thailand and India have been effectively turned into giant parking lots as COVID-19 travel restrictions choke demand.

"If you have got those aircraft on the ground, you can imagine to get them back up and running in a short space of time is no easy thing," said Gary Moran, head of Asia aviation at insurance broker Aon. "The challenge is you can have a typhoon or hurricane coming and there are going to be a lot of aircraft that aren't going to be able to be moved in time."

Airline insurers, already on the hook to refund large portions of crash risk premiums because of the groundings, now face the larger-than-usual risk posed by having lots of airplanes grouped together at airports, industry experts said.

"One event could create damage which costs millions to repair, maybe even closer to hundreds of millions depending on the aircraft that are involved," said James Jordan, a senior associate at law firm HFW's Asia aerospace and insurance practices.

In guidance to be issued to airport operators this week, seen by Reuters, the trade group Airports Council International (ACI) warns that flying the planes out of danger, the practice in normal times, may not be possible. It says extra precautions such as more tie-downs could be needed.

"Extreme weather events such as hurricanes, typhoons and cyclones are a seasonal hazard in many areas of the world, and in the COVID context provide an additional layer of hazard with many airports accommodating larger numbers of parked aircraft," ACI Director General Angela Gittens said in a statement to Reuters.

Manila's Ninoy Aquino International Airport has so many aircraft on the ground that is using a runway for parking, according to a spokesman for the Civil Aviation Authority of the Philippines.

Osaka's Kansai International Airport, whose runway flooded when Typhoon Jebi breached a seawall in 2018, said it had raised the wall's height and waterproofed facilities.

Airports will also need to ensure they do not have any loose equipment that poses a risk to airplanes or they could face claims from airline insurers, Aon's Moran said.

"The airport is supposed to maintain a safe environment for the aircraft," he said. "That is their duty of care."

Mumbai's airport said on Wednesday that small private planes vulnerable to strong winds had top priority to be flown out or parked in a hangar as the city braced for a rare cyclone.