International Air Transport Association Director General Willie Walsh said strong freight revenues had been "the difference between life and death for some airlines" as COVID-19 lockdowns brought passenger traffic to a standstill.

"Cargo will continue for the next few years to play a bigger role than it did before the crisis," he told an online briefing.

The mass grounding of passenger planes that normally carry half the world's air freight in their holds has driven cargo prices and revenue higher. That led some airlines to post record freight earnings last year, even as overall losses peaked.

Despite returning passenger capacity, a broader economic recovery will sustain cargo income that surged to 35% of airline revenue last year from 10-15% pre-crisis, IATA predicts.

Major airlines like Lufthansa are also counting on further support from the historically volatile freight business.

"Even if there's more passenger aircraft coming (back), the global economy will pick up further," CEO Carsten Spohr said during the German airline's results presentation last month.

"We never know with cargo. But we are at least optimistic," he added. (This story refiles to delete repetition of Walsh comment)

(Reporting by Laurence Frost in Paris and Sarah Young in London; Editing by William James and Alexander Smith)