The lack of available runway capacity in the U.K. will limit airlines’ abilities to explore new markets and will drive up ticket costs, the country’s Civil Aviation Authority (CAA) warns.

The message comes as the U.K. government works on defining an aviation policy that is due to be unveiled in the spring. The CAA says that “while London is well connected now, capacity constraints at London’s airports may already mean that their airlines are less able than those at other European airports to try out new routes to emerging markets. The lack of available capacity at Heathrow is already beginning to affect the U.K.’s air services agreements with foreign states.”

And, adds Iain Osborne, director of regulatory policy at the CAA, looming “capacity constraints mean airports may become increasingly specialized in the routes they offer and the airlines that fly them.”

The CAA writes that “at present, most people in the U.K. have excellent access to airports, with around 90% of the population living within two hours’ travel of at least two airports serving international destinations and 70% within one hour of one airport. This level of choice is currently unrivaled in Europe.” However, it adds, “that position will soon be tested by increasing capacity constraints in the Southeast, which will increasingly limit the choice and value of available flights. Limited supply means the price of air travel is likely to rise.”

Another message the CAA is sending the government is that high-level objectives should be set for industry, but that companies should be allowed to figure out how best to address them, rather than being subjected to a heavy regulatory approach.

The CAA urges the government to make sure consumers are at the core of its policy; it believes they could be hurt if capacity issues are not addressed.