The challenges confronting the global aviation sector amid Covid-19 will continue for the foreseeable future, according to the International Air Transport Association (Iata).
The industry group noted last week that the recovery in passenger traffic has been slower than expected as the coronavirus rages in cities worldwide.
Global passenger numbers this year are expected to decline by 55 per cent compared with last year, worse than the 46 per cent forecast in April, Iata said.
Numbers will not return to pre-Covid-19 levels until 2024, a year later than what was previously projected, it said.
Chief executive and director-general Alexandre de Juniac said: "Passenger traffic hit bottom in April, but the strength of the upturn has been very weak.
"International markets remain largely closed... And in many parts of the world, infections are still rising. All of this points to a longer recovery period and more pain for the industry and the global economy."
Iata noted that there is little sign of virus containment in many important emerging economies.
These economies, together with the United States, make up about 40 per cent of the global air travel market. Their continued closure, particularly to international travel, has significantly slowed recovery.
It added that weak consumer confidence, along with reduced business travel, will further hamper the industry's efforts to recover.
Iata said: "While historically, GDP growth and air travel have been highly correlated, surveys suggest this link has weakened, particularly with regard to business travel, as video conferencing appears to have made significant inroads as a substitute for in-person meetings."
Experts have warned that the slow recovery will lead to inevitable job cuts, given that most airlines are now overstaffed.
Some airlines have already started slashing jobs, with more expected to follow in the coming months.
Hong Kong carrier Cathay Pacific recently offered early retirement to certain pilots. This is on top of short-term measures, including executive pay cuts and two rounds of a voluntary special leave scheme.
Cathay is undertaking a comprehensive review of all its operations, with recommendations on the future size and shape of the airline expected by the fourth quarter.
Significant job cuts have also taken place in the Middle East, where carriers were booming before the Covid-19 pandemic.
The BBC reported that Dubai-based Emirates is set to cut as many as 9,000 positions.
Qatar Airways has also warned of substantial job losses and has implemented pay cuts.