Delta is set to expand its network from Seattle next spring, introducing new and increased service across several markets.
Beginning May 7, 2026, the airline will launch brand-new daily nonstop flights between Seattle and Philadelphia — a route the airline says has been highly requested by both corporate and leisure travelers. Flights will be operated by an Airbus A321neo.
American and Alaska currently link the two cities with non-stop flights.
On the same date, Delta will move up the start of its fourth daily Seattle–Boston flight, which was originally scheduled to begin in June.
An airline spokesperson confirmed the network additions to AirlineGeeks on Friday.
West Coast Service Boost
The airline will also add frequencies on two West Coast routes. Service from Seattle to Ontario, California, will increase to four times daily, while San Jose, California, will grow to five times daily.
“Seattle continues to be one of Delta’s most important coastal gateways, connecting customers to key business and leisure destinations across the country and around the world,” said Amy Martin, Delta’s network planning chief, in a statement. “Philadelphia has been a top-requested destination from our Seattle corporate customers, and this new service reflects our commitment to investing in the routes that matter most to them while building an even stronger network from the Pacific Northwest.”
