Traffic at airports operated by BAA rose by 4 percent in March, compared with the same month in 2011, helped by Easter being earlier this year and strong growth on routes to emerging markets.
BAA, which is Britain's main airport operator and majority owned by Spanish infrastructure group Ferrovial, on Wednesday said 8.6 million passengers travelled through its airports last month.
The company said 5.7 million passengers passed through London Heathrow - Europe's busiest airport - last month, 6.9 percent up on last March.
That increase means Heathrow saw more than 70 million passengers over a twelve month period for the first time, BAA Chief Executive Colin Matthews said in a statement.
Traffic from Heathrow to the BRIC (Brazil, Russia, India and China) countries saw growth compared with March last year, with an increase of 62.3 percent in traffic to and from Brazil.
BAA said Heathrow's performance was particularly notable for the 4.2 percentage point increase in load factor - how full planes leaving the airport are - to 73.4 percent compared to March last year.
The increase was also helped by Easter being earlier this year, with a substantial proportion of pre-Easter traffic falling in March rather than in April last year.
(Reporting by Rhys Jones; editing by Adveith Nair)