Airlines in Asia are raising ticket prices and mapping out contingency plans that include grounding planes as the escalating Middle East conflict threatens to trigger the worst oil shock since the 1970s.

Indian carriers have hiked prices on long-haul routes by 15% and are considering further increases, people familiar with the matter said. In Vietnam, state media warned airfares could increase as much as 70% given the country’s reliance on imported jet fuel.

Meanwhile, Hong Kong Airlines said Tuesday it will raise fuel charges from March 12 across a range of routes. That includes a HK$5 increase in the surcharge on mainland China flights and HK$150 for long-haul trips to places like North America.

Airlines in the region are not as well hedged against high oil prices as rivals in Europe or the United States, making them more vulnerable to sudden surges in jet fuel prices. That has prompted low-cost Southeast Asian carriers to think about grounding planes if jet fuel became unaffordable or inaccessible, according to people familiar with the matter.

After surging toward US$120 a barrel on Monday, oil then fell after US President Donald Trump signalled the war will end soon.