A plane taking off from Reagan National Airport. (Ricky Carioti/The Washington Post)

Thanks to the American Airlines/USAir merger, which forced the airlines to give up 52 slot pairs at Reagan National Airport, travelers in the D.C. region will have some new — and potentially lower-cost — flight options.

(Note: If your travel plans take you to Dallas, you’ll be especially happy to hear what the airlines have planned).

But the changes will also pose issues for Reagan National Airport, which set an all-time record for traffic in 2013, with 20.4 million passengers flying through its gates. As a result of changes because of  the merger, the number of passengers could grow by 2.4 million, straining an airport that has little room to expand.

The airport has invested $37 million to expand its historic Terminal A, adding an additional security screening area in hopes of getting folks to their flights more quickly. But in the newer Terminals B and C, crowds will likely grow as folks flock to the closest airport to downtown D.C.

JetBlue, Southwest and Virgin America are among the carriers that picked up slots as a result of the merger.  Already JetBlue has announced new service beginning in June to Charleston, S.C., Hartford, Conn., Nassau, Bahamas and Tampa, Fla. Southwest Airlines also said they will start a new daily non-stop flight to Dallas Love Field. They’ll announce more flights in May.  For its part, Virgin America announced that it will offer four daily nonstop flights to Dallas Love Field beginning in October.

At Dulles, the picture hasn’t been so bright — especially when it comes to domestic traffic. Between January 2013 and January  2104, the number of domestic travelers dropped by 6 percent to 14.7 million. But the number of international passengers grew 4.4 percent to 7 million.

Airport officials said two airlines will start new international routes in 2014. United will offer daily service to Madrid, Spain, starting June 4 through Sept. 6. The airline will offer service to the Bahamas on Saturday and Sunday beginning June 7 through Aug. 17.

And beginning June 10, Air China will offer four flights a week from Dulles to Beijing.