Demand for travel in via Heathrow January was weaker than expected and more than 56% down versus pre-pandemic levels.
The hangover from the Omicron Covid variant continued to suppress passenger confidence.
More than 1.3 million passengers cancelled or did not book their trips because of Omicron restrictions in December and January. The airport handled 2.6 million passengers last month.
While bookings for outbound tourism are recovering, inbound trips and business travel remain weak.
The London hub cited Covid-19 levels in the UK and other countries, international testing requirements and the risk of new border closures in the event of a new variant of concern.
Heathrow is maintaining its forecast for the year at just over half of pre-pandemic levels “on the basis that strong demand for outbound summer holidays can offset a weaker start to the year.”
It is working with airlines and ground handlers to increase resources across the airport ahead of the summer peak.
A spokesperson said: “We urge the government to support the sustainable recovery of travel and trade by outlining a playbook for managing future variants and seeking international harmonisation of travel rules.”
Chief executive John Holland-Kaye said: “After a tough Christmas, Omicron has continued to bite and this has been a weak start to the year.
“As short-lived as the additional travel restrictions were, they ruined the travel plans of more than 1.3 million passengers in the last two months.
“Today’s removal of restrictions for vaccinated passengers in and out of the UK offers a ray of hope, but the Omicron hangover proves demand remains fragile, and at risk to new variants of concern and government needs to set out a playbook for managing future variants that allows travel and trade to keep flowing.”
Heathrow said it was continuing working with the Civil Aviation Authority on a better regulatory outcome for consumers by correcting the “factual errors” in its initial proposals and designing effective mechanisms to enable the fastest possible traffic recovery.
Meanwhile, Martin Chalk, general secretary of pilots union Balpa, said: “Whilst there is some way to go in the industry’s recovery, and we urge government to do all it can to restore confidence and provide the right supportive environment for that recovery, pilots are already training and flying to take people all over the world, safely and in comfort.
“Having spoken with ministers on a number of occasions recently, I am confident that they fully support our members and our industry to do what it does best; connect families, connect business, connect people.”