Flight Global is reporting that Ronald Reagan Washington National airport (DCA), one of the four major airports that uses a slot-system to limit flights, actually has unused runway capacity:

Unused runway capacity at Ronald Reagan Washington National airport could be used to add additional flights, finds the US government.

The Government Accountability Office (GAO) found that there were only about 53 take-offs and landings per hour in April 2012 compared to a maximum capacity of 67 movements, in a report looking at the impact of eight new beyond-perimeter slot pairs at National on the Washington DC area airports that was released earlier this month.

The shortfall is attributed to a decline in general aviation and unscheduled flights after the 11 September 2001 terrorist attacks, according to the report. There were on average 17 of these movements per day in 2011, which is down from about 210 prior to 2001.

What DCA does not have though is adequate terminal capacity to handle more flights, but that’s something that can be addressed.

CLT impact: US Airways is the dominate carrier at Reagan National. Should extra slots be created at DCA, some would likely go to US Airways. The aircraft to fly those routes would have to come from somewhere, and there are only three options: Charlotte, Philadelphia, or Phoenix, with Charlotte being US Airways’ largest hub. Of course, extra DCA slots could also help push the airline to order more planes…