Newcastle airport fears an independent Scotland could damage its future.
The airport is concerned a Scottish government would half APD if it’s granted independence, before eventually abolishing the tax, this could mean travellers making the journey across the border for flights.
APD is a duty which is charged on the carriage of passengers flying from a UK airport. For short haul flights each passenger is charged £13, and £69 for longer flights.
In April at a debate organised by Scotland’s travel trade body, the Scottish Passenger Agents’ Association (SPAA), politicians and campaigners from both the “yes” and “no” campaigns pledged to slash APD if they win the autumn vote.
Newcastle Airport planning director Graeme Mason told the BBCthat customers are mobile and will “shop around” for the cheapest flight and are prepared to travel “quite long distances to get those flights”.
The airport wants the UK Government to offer assurances that it would offer help to the airport should Scotland vote for independence in September.
"There are a number of options open to the government. They could abolish APD altogether, or they can match any reductions made by Scotland,” said Mason.
"But if they don't do this the North of England is going to be at a serious disadvantage to the rest of Scotland."
Pro-independence group Business for Scotland said if it gained independence and scrapped APD then it would be a benefit to the northeast of England.
"Scotland is doing what it should be doing; we're bringing ourselves into line with other countries across Europe who have much lower levels of Air Passenger Duty than we currently have,” spokesman Ivan Mckee said.
"It's the best thing for the Scottish economy to do, and a growing Scottish economy would be good for the northeast of England.”
Extra funding for Newcastle airport could come from the Government’s Regional Air Connectivity fund, which last week agreed a £2.85 million deal to secure flights between London Stansted and Dundee airport.