United Airlines will increase capacity on 18 routes from its San Francisco hub beginning in June, including eight markets where competitor Alaska Airlines plans to expand.

The Chicago-based Star Alliance carrier will add one additional frequency to Seattle for 10 daily flights from 1 August; one to Albuquerque, Baltimore/Washington, Indianapolis and Nashville for two flights from 15 August; one to Kansas City and Philadelphia for three flights from 15 August; and one to Portland (Oregon) for nine flights from 15 August, United says.

United will operate Airbus A319s with 128 seats on the new flights to Baltimore, Indianapolis, Nashville, Portland and Philadelphia, Airbus A320s with 150 seats to Seattle, and Embraer 175s with 76 seats to Albuquerque and Kansas City.

All of the markets receiving additional service are either Alaska Airlines hubs or ones the carrier, as well as its subsidiary Virgin America, plan to add from San Francisco during the next five months. Portland and Seattle are Alaska hubs, while it plans to begin service to Philadelphia in August; Albuquerque, Indianapolis, Kansas City and Nashville in September; and Baltimore in October.

United will also shift select flights to 10 destinations from San Francisco to mainline aircraft in June. An A319 will fly to Santa Barbara from 8 June; an A320 to Calgary, Dallas/Fort Worth, Kansas City and Minneapolis/St Paul from 8 June and to Bozeman from 1 July; and Boeing 737s to Burbank and Palm Springs from 8 June, Sacramento from 1 July and Fresno from 15 August.

“These additional flights and larger aircraft to new cities and those already part of our network will offer customers even more convenient flight options and easy connections to popular destinations around the US and Canada,” said Mike Hanna, vice-president of United's San Francisco International Airport hub, in a statement.

United has already announced new service to Hartford, Sonoma County and Spokane from San Francisco beginning 8 June.

With the latest capacity additions, seats at the carrier's San Francisco hub are scheduled to increase 6.35% in the third quarter and 4.54% in the second half compared to the same periods in 2016, FlightGlobal schedules show.

In addition to Alaska and Virgin America, United competes with American Airlines to Philadelphia and Delta Air Lines to Seattle, the schedules show.

Source: Cirium Dashboard