Passenger numbers on flights more than halved at Ryanair (RYA.L) and dropped 41% at Wizz Air during peak summer season in August, according to the airlines.
Ryanair flew just seven million passengers in August, down 53% from 14.9 million the previous year.
Figures published by the company on Wednesday indicate it flew just 60% of its usual August schedule, with a load factor—a measure of how many seats are used—of just 73%.
But the data marked an improvement for the company versus the previous month, with passenger numbers down 70% year-on-year in July. It had run 40% of its usual schedule.
At Wizz Air, passenger numbers dropped to 2.38m, with a load factor of 70.9%.
Airlines have hit out at the UK government over travel quarantine policy announcements over the summer, including popular destinations like France and Spain, for exacerbating their woes.
Ministers have introduced the measures for countries where new coronavirus cases have risen above certain levels. But Ryanair’s boss Michael O’Leary has claimed the 14-day quarantine rules are “useless and ineffective.”
Surveys and booking data suggest the restrictions heavily deter travel to affected countries.
The International Air Transport Association (IATA), which represents airlines worldwide, also hit out at quarantine policies and border closures on Tuesday.
“Airlines have been largely grounded for a half-year. And the situation is not improving,” said Alexandre de Juniac, its director-general and CEO.
“In fact, in many cases it is going in the wrong direction. We see governments replacing border closures with quarantine for air travelers. Neither will restore travel or jobs.
“Worse, governments are changing the entry requirements with little notice to travellers or coordination with their trading partners. This uncertainty destroys demand.”
The IATA said four in five potential travellers had stayed at home, with total July traffic down 79.8% on the previous year.
It called for more government support for airlines, and for widespread COVID-19 testing measures to reduce virus risks and enable more re-opening of borders.
“Many airlines will not have the financial means to survive an indefinite shutdown that, for many, already exceeds a half-year,” added de Juniac.
Meanwhile British MPs have called for the UK government’s furlough scheme to be extended for the aviation industry, with alarm over its wind-down.