Newcastle airport fears losing thousands of passengers a year if Scotland votes for independence.
The airport is concerned about the Scottish government’s potential plan to halve Airport Passenger Duty before abolishing it, prompting passengers to head north of the border to get the cheapest flights.
If an independent Scotland abolished APD, it is estimated that a family of four on a flight to the US could save £276 on their fare.
The airport wants the UK government to offer assurances that it would step in to help the airport should Scotland vote for independence in September.
Newcastle Airport planning director Graeme Mason told the BBC: “Customers are very mobile; they’ll shop around for the cheapest flight and they’ll travel quite long distances to get those flights.”
He added: “There are a number of options open to the government. They could abolish APD altogether, or they can match any reductions made by Scotland.
“But if they don’t do this the north of England is going to be at a serious disadvantage to the rest of Scotland.”
However, pro-independence group Business For Scotland says the northeast of England would benefit from increased investment if Scotland abolished APD.
Spokesman Ivan Mckee said: “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.
“It’s the best thing for the Scottish economy to do, and a growing Scottish economy would be good for the northeast of England.”