Stansted was the group's fastest growing airport with a 35 per cent surge in passenger numbers to 7.4 million.
This represented an increase of 1.9 million passengers, which was only just behind the extra 2.2 million at Gatwick and 2.9 million at Heathrow.
"In the past Stansted was so small that even 35.4 per cent growth would have had little impact on BAA's figures," the company noted.
"Stansted is now firmly established as a major force in the London airports system."
In March the Essex-based airport handled 644,900 passengers, 57.8 per cent more than the same month in 1998.
The airport has benefited from the scarcity of slots and higher handling and landing charges at Gatwick and Heathrow.
It has also attracted budget airlines such as British Airway's Go and Ryanair.
The success made up for a 5 per cent fall in passengers passing through Aberdeen in March, which BAA said was due to a fall in pre-Easter business traffic and "an uncertain oil market". Over the 12 months it grew just 0.5 per cent.
Overall BAA's seven airports, which also include Aberdeen, Edinburgh, Glasgow and Southampton achieved a 7.6 per cent annual rise.
European scheduled traffic grew by 9.2 per cent, with routes to the Irish Republic seeing the fastest growth rate of 13 per cent.
New capacity and competitive air fares boosted the North American market by 9.7 per cent.
But the impact of the slump in South-east Asia and Japan held back growth of other long-haul services to 6.3 per cent.Reuse content