WASHINGTON — United Airlines has started seasonal service from Dulles International to Barcelona, Spain and Portugal’s capital, Lisbon. They’re the first-ever nonstop flights to the two cities from a Washington-area airport.

United’s daily service to Barcelona will be operated through Oct. 29. Daily flights to Lisbon will go through Sept. 6.

Dulles continues to expand its international offerings. Earlier this month, LAN Peru began direct flights to Lima and Air Canada began its first service from Dulles with three daily nonstop flights to Toronto.

Dulles is the dominant airport for international flights in the Washington area, with 120 destinations serving 51 countries.

Dulles also reversed four straight years of passenger declines last year, with 21.7 million passengers. International traffic at Dulles rose to a record 7.2 million passengers in 2015.