MAG is calling on government to present specific and practical proposals to maximise the potential of other airports after MPs voted to back a third runway at Heathorw.
This is because new capacity at Heathrow is more than a decade away.
The call came as new long-haul routes helped MAG airports achieve their busiest ever June with passenger numbers up by 6.4%.
MAG chief executive Charlie Cornish said: “June’s figures demonstrate the strength of demand from both passengers and airlines to fly from our airports, and increasingly to more long-haul, global destinations. We have the potential to deliver many more direct long haul services in the years to come.
“The government’s support for airports looking to make the best use of existing capacity provides a clear framework for growth, and it is critical that it now matches its backing for Heathrow expansion with specific and practical proposals to improve rail access and maximise the potential of airports like Manchester, London Stansted and East Midlands.
“Manchester and London Stansted are the two largest UK airports with significant runway capacity and our investment will allow us to meet continued demand for aviation growth both in and out of the UK.”
Stansted saw 11.3% year-on-year growth to handle 2.6 million passengers last month, driven by a new daily Emirates service to Dubai.
Manchester airport traffic returned to growth, bouncing back after Monarch Airlines’ collapse in October 2017.
The airport grew 3.4% to serve 2.8 million passengers in June, as Monarch’s runway slots were filled by other airlines including Jet2.com, Thomas Cook Airlines, Tui and easyJet.
Meanwhile, routes to Muscat and Dubai and to the US proved popular.
Summer holiday destinations to watch for this season, based on passenger numbers compared with last June, are Antalya, Dalaman, Cancun and Ibiza.
East Midlands airport grew slightly year-on-year by 0.1% as the airport handled 560,000 passengers.
The three most popular destinations from East Midlands in June were Palma, Alicante and Malaga, while the destination that was most popular compared with last year was Dalaman in Turkey.