Stansted airport has seen a 7.6% rise in passenger numbers with nearly 1.82 million people passing through the airport last month compared with May 2013.
The announcement of passenger levels came as the Whitehall-appointed Airports Commission published its latest discussion paper entitled Utilisation Of The UK's Existing Airport Capacity.
The commission reaches no conclusions in its paper and is now seeking the views of interested parties.
The commission is also studying the so-called "Boris Island" option of a new airport in the Thames Estuary - a project favoured by London mayor Boris Johnson.
The commission is due to make its final recommendation to ministers in summer 2015 but at a date after the general election in May.