Heathrow marked a year since the first Covid-19 lockdown with an 82.6% passenger slump.
The London hub reported a year-on-year fall in March to just 542,000 passengers.
Key transatlantic routes suffered one of the deepest declines at 92.7% over March 2020, just behind the 93.9% drop to Latin America.
Traffic to the European Union was down by 84% and almost 76% to Asia Pacific.
The total number of aircraft movements dropped by 63.4% to less than 9,500 in the month.