Proponents of relaxing medium-haul restrictions at Washington National have vowed to take their fight to the US Senate after suffering a setback when the US House of Representatives rejected their attempt to allow more long-haul flights at the airport.

The Capital Access Alliance (CAA), a coalition of business and transportation leaders supported by Delta Air Lines (DCA), said: "This fight is far from over". "Changing the status quo is never easy, and we've seen how aggressively opponents of reform react to threats of more competition and lower prices for consumers. Fortunately, it's clear there is strong bipartisan support in both the House and the Senate for a consensus solution that will boost competition, give consumers more choices and make air travel to Washington, DC, more affordable and accessible," said CAA spokesman Brian Walsh. "As this debate moves to the Senate, we will continue to elevate the voices of Americans who are suffering from high ticket prices and a lack of access to their nation's capital."

The House of Representatives late on July 19 voted 229 to 205 against a proposed amendment to the Federal Aviation Administration (FAA) Reauthorisation Bill that called for adding seven daily roundtrip flights at DCA inside and beyond the so-called "DCA Perimeter Rule" - a rule from 1966 that limits the number of flights that can land or take off each day outside a radius of 1,250-miles (2,011 kilometres). The CAA coalition first sought to add 28 daily flights but later settled on seven. Only seven airlines are authorised to operate just 20 daily round trips to 10 beyond-perimeter destinations to/from the airport, meaning that 40% of passengers must make at least one connection when flying to or from DCA.

CAA member Delta Air Lines has been advocating for the modernisation of the perimeter rule, arguing it is stifling competition, making travel to the capital longer, more expensive and more harmful to the environment.

However, American Airlines, United Airlines, and Alaska Airlines oppose changes to the slot and perimeter rules at DCA, citing FAA and Metropolitan Washington Airports Authority concerns that added flights would dramatically increase passenger delays and "erode the operational integrity of the airport".