IAG fell as much as 16%, the most since March 16, 2020, when lockdowns went into effect across the world, and was down 4.5% at 10:14 a.m. in London. Ryanair Holdings Plc dropped as much as 7.4% while EasyJet Plc slid as much as 10%.

“Airlines and travel operators had seemingly refused to countenance the cataclysmic idea of another heavily disrupted summer and had been busily advertising to an increasingly inoculated U.K. population,” said Russ Mould, investment director at AJ Bell. “The travel sector is waking up on Monday to a dose of reality.”

Airlines in Europe have been lobbying to restart flights over the normally busy summer season, following months of lockdown measures and travel bans that wiped out their balance sheets. Last week, the European Commission unveiled a plan for the introduction of a digital pass that would ease travel for those who have been vaccinated, recovered from the virus or recently tested negative.

Still, those plans may be premature after France and other governments announced new lockdown measures in several regions to stem a third wave. On Saturday, Mike Tildesley, a scientist on a U.K. government advisory body, told the BBC that summer holidays overseas were extremely unlikely because of the risk that travelers could bring new variants back to the country.

The latest measures — along with confusion over testing and quarantines, and the fact that young people are still to be vaccinated — mean that “most of the expectations of summer are implausible and imponderable,” Citigroup analysts led by Mark Manduca wrote in a note to clients Monday. “Summer in our view will be anything but normal.”