Wizz Air reported an operating profit of €57 million in the three months to end September. In the half, revenues surged 87% on 2020 levels to €880 million.
But bosses forecast a €200 million operating loss for this quarter that "may carry over" into 2022.
It comes after rival Ryanair also announced it would cut prices to stimulate demand over winter, after turning a profit this summer.
CEO József Váradi told Bloomberg he expects bookings to surge again from Spring 2022.
In a statement, he said the company remains in "investment mode", and is growing its fleet.
He said: "We are still in an investment mode in the current quarter as we bring on additional fleet and crew ahead of a fully utilized operation from Spring 2022 onwards.
"We are stimulating demand with pricing given the continued impact of COVID-19. Additionally, FX and commodity markets continue to be volatile and are impacting our financial performance."
Shares held steady at around 4829p in early trading. Wizz shares have gained 5.8% this year.