The group said the growth had been strongest in Stansted which rose by 5.8% to 1.99 million passengers, with Belfast, Copenhagen and Frankfurt driving the increase.
Manchester was second placed, with the airport reporting an increase in passenger numbers of 3.7%, but also giving it a total of 1.99 million passengers.
The airline is seeing growth from Jet2.com, Thomas Cook Airlines and Tui, that have filled the gap left by the collapse of Monarch while Jet2.com is also extending its operations into Terminal 2 for the first time, giving it access to two terminals.
However, the success was marred by East Midlands airport which saw a 1.7% decline in passenger numbers to 272,000.
MAG corporate affairs director Tim Hawkins said it is hoped the arrival of a new managing director, Karen Smart, who joins from Stansted, will help turn the airport’s fortunes around this summer.
The March figures mean MAG has now served 58.9 million passengers in the financial year to March 2018.
Hawkins said: “London Stansted’s growth demonstrates the key role it plays in connecting London and the East of England to an unrivalled range of European destinations.
"It was encouraging to see that the fastest growing routes at Stansted in March were those that had a strong mix of business passengers."