The coronavirus crisis will lead the airline industry into record annual losses of $84 billion as 2020 goes down as the "worst year in the history of aviation," the sector's main global body predicted Tuesday.

Airline passenger traffic is expected to rise 55% in 2021 from its depressed level this year, while still remaining 29% below its 2019 level, the International Air Transport Association (IATA) said in an updated forecast.

As an air travel recovery gathers pace in Asia and takes root in Europe and North America, airlines are counting the cost of many weeks of lost business, an increased debt pile and a diminished outlook for future demand.

"Financially, 2020 will go down as the worst year in the history of aviation," IATA Director General Alexandre de Juniac said.

IATA predicted a further $15.8 billion hit to the industry's bottom line in 2021 - for a total of about $100 billion in losses largely attributable to the pandemic - as recovering traffic remains well short of pre-crisis levels, and airlines slash fares to win business.

Even in markets where COVID-19 infection rates have fallen sharply, airlines are still confronted by a patchwork of remaining travel restrictions and consumer wariness.

A British 14-day quarantine introduced for arriving passengers this week has prompted an angry response and threats of legal action from the broader travel industry, amid reports that the regime may soon be loosened in favour of "air corridors" to agreed destinations.

IATA is urging governments to refrain from quarantine measures that deter most travel, arguing that on-board safety measures including mandatory facemasks are adequate.

"These measures should give governments the confidence to open borders without quarantine measures," De Juniac said.