The U.K. government should draw up a long-term aviation policy that also includes adding runway capacity in the south east of England, the country’s civil aviation authority argues in a new report.

“Developing appropriate additional capacity would deliver significant benefits to consumers and wider benefits to the U.K. economy,” the Civil Aviation Authority (CAA) says. The U.K. government, which is in the process of trying to define an aviation policy, has been reluctant to including additional runways around London as part of the plan. Other measures to maximize runway capacity or shift some transport to rail are seen as having utility, but the CAA characterizes such steps as “essentially short-term fixes” that “are not enough to maintain the U.K.’s direct access to global markets alone without additional runway capacity.”

The CAA also pours cold water on the idea of using existing capacity by focusing it on long-haul operations. Any future policy “should seek to ensure that the very high levels of short-haul connectivity that consumers enjoy are at least maintained at current levels, it argues.

“Additional capacity would offer significant benefits for consumers, and for the U.K. as a whole, so long as it is delivered in an environmentally sustainable way,” CAA Chief Executive Andrews Haines argues in announcing the completion of the “Aviation Policy for the Future,” the third in a series of inputs it is providing to the government as part of the policy planning process.

The CAA warns that left unaddressed, the current situation is likely to see ticket prices increase and route choice drop. By 2030, the capacity constraint could add £10 ($15.48) per passenger on a return fare, the document states.

“The challenge facing the Government is to create an aviation policy that stands the test of time—not a policy for five years, but one for thirty years,” Haines argues. “If the private sector is to have sufficient confidence to deliver additional capacity then it needs to be convinced that government policy is based on robust evidence and is likely to last for at least a generation.”