By Anthony O. Goriainoff

London's Heathrow Airport said Tuesday that its pretax loss narrowed for the first nine months of 2021 as passenger numbers rose in the third quarter but it doesn't expect air traffic to fully recover for another five years.

The airport--jointly owned by the Qatar Investment Authority, China Investment Corp., Spain's Ferrovial SA, and other investment companies--said that passenger and cargo numbers recovered to 28% and 90% respectively of pre-pandemic levels. Still the airport said that traffic was not expected to fully recover until at least 2026.

For the nine months ended Sept. 30, its pretax loss was 1.38 billion pounds ($1.90 billion) compared with a loss of GBP1.52 billion for the first nine months of 2020.

Revenue for the period fell to GBP695 million from GBP951 million in the year-prior period. The company said that third-quarter revenue increased by 45% compared to the third quarter of 2020, and that this was a reflection of the increase in passengers.

"Our liquidity position remains strong with GBP4.11 billion of cash as of Sept. 30 2021, which provides sufficient cash to meet all obligations into 2025 under our base case traffic forecast or until February 2023 in the extreme no revenue scenario," Heathrow said.

Write to Anthony O. Goriainoff at anthony.orunagoriainoff@dowjones.com