Cheap flights from the East of England's airports are losing the region's economy about £1.9bn a year, a campaign group has said.
Many budget airlines fly from Stansted Airport in Essex
Friends of the Earth said residents spent about five times more abroad than foreign visitors flying into the East.
The situation could get worse if the East's airports - Stansted, Norwich, Southend and Luton - expand, it said.
The British Air Transport Association said there was no evidence that airport expansion hurt the economy.
Friends of the Earth's report said foreign visitors spent about £517m a year in the region, while East of England residents spent about £2.4bn a year abroad.
Friends of the Earth said airport expansion could increase the amount of money spent abroad, while the region's tourist destinations such as Great Yarmouth, Cromer and Felixstowe were particularly likely to suffer.
Friends of the Earth's East of England campaigner, Mary Edwards, said: "We know airport expansion is bad for the environment. These figures show it is bad for the East of England's economy, too.
"Local businesses are missing out on millions of pounds every year and airport expansion will make this worse, encouraging people to take more and more short trips abroad."
But business leaders criticised the findings.
John Cridland, CBI deputy director-general, said the report had painted an "incomplete picture".
He said: "UK aviation is one of the country's most successful industries, contributing over £10bn to the economy and directly employing over 180,000 people.
"Without a successful aviation industry, our businesses would find it more difficult to compete globally, and the UK would lose out on vital inward investment."