Passengers flying from some regional airports are being charged twice for services, an air watchdog has said.
Norwich International Airport introduced passenger fees in April
The Air Transport Users Council says growing numbers of airports are charging fees to cover development and security on top of their ticket prices.
Norwich International Airport is the latest to introduce a charge for all passengers flying from its terminal.
Airports say the revenue is needed to provide better facilities and to deal with the heightened terrorist threat.
The chief executive of Norwich Airport, Richard Jenner, told BBC Radio's Five Live Breakfast the charge was the "only way" to could raise needed funds.
"We've expanded 30% two years running, and it's fine for airports if there's a lot of spare capacity. But we've had to expand the size of aprons, the size of the departure lounge.
"We also need to invest in facilities which have been under-invested in for many years."
Airport Development Fees (ADF) have already been introduced at Newquay Cornwall Airport, where all passengers over the age of 16 have been charged £5 since 2005.
Norwich International followed in April this year. It charges adults £3 while children aged between two and 15 must pay £1.
Fees 'for investment'
When the fees were introduced, the airport's bosses said the money would be used to make improvements to the runway as well as check-in areas, shops, parking and customer services.
Liverpool John Lennon Airport is also due to trial a fee for passengers who want to be fast-tracked through security.
The Air Transport Users Council and airlines say they are concerned about the additional passenger charges.
They claim airport customers are already paying for airport development and security in their ticket prices.