WASHINGTON — Dulles International Airport had more passengers than Reagan National Airport in 2018. That’s the first time it’s passed National in four years.

For the year, Dulles saw 24.1 million passengers, compared with 23.5 million at Reagan National. For Dulles, that was 1.4 million more passengers than 2017. For Reagan National, it was about 400,000 fewer passengers.

Combined, the two airports served 47.5 million passengers in 2018, up 1.6 percent from 2017.

The gains at Dulles were driven by a surge in both international and domestic flights. Domestic travel at Dulles was up 6.3 percent, fueled by new flights from Frontier Airlines, Southwest Airlines and United Airlines.

United has added 12 new domestic routes for Dulles in 2018 and 2019.

Dulles also picked up several new international routes in 2018, including United service to Edinburgh, Scotland; Cathay Pacific Airways nonstop service to Hong Kong (the longest nonstop route from Dulles); Volaris nonstop service to San Salvador; and increased passenger counts on Aer Lingus, Air Canada, Emirates and Air China.

Dulles also will get a bump this year with new airlines and routes, including nonstop United services three times a week to Tel Aviv starting in May; Alitalia service five times a week to Rome, starting in May; and TAP Portugal’s new five weekly flights to Lisbon, Portugal, starting in June.