While crude oil prices fell as much as 16% to below US$100 a barrel Wednesday after Trump announced the ceasefire, the chief executive officers of Malaysia Aviation Group and Thai Airways International Pcl said the impact on prices and supply concerns will remain.

“Even if the war stops, it’s going to take many, many more months for the price to stabilise,” Malaysia Aviation’s Nasaruddin Bakar said at an International Air Transport Association event in Singapore.

Carriers globally are grappling with a more than doubling of jet fuel costs since the war broke out, and the threat of supply shortages in some regions has forced some airlines to reduce services.

Thai Airways CEO Chai Eamsiri said this is the worst oil shock in his near-four decade career.

“This is the worst one,” he said. “This time is about the infrastructure that was destroyed. It will take some time to call back all the supply, the facilities, the refinery, the infrastructure.”

Malaysian low-cost carrier AirAsia X Bhd earlier this week said it had increased fares as much as 40% and hiked fuel surcharges to cope with the price shock.

In the US, United Airlines Holdings Inc has trimmed roughly 5% of capacity. Air New Zealand Ltd has pushed through a second round of cuts to flight schedules and further increased fares to manage with higher oil prices.