Cheap flights from Seattle to Denver (SEA to DEN) from $351

The cheapest month to fly is September, and departing on Saturdays typically offers the best fares. Book 6–8 weeks ahead for the best prices.

Book at the right time: For domestic routes like Seattle to Denver, the sweet spot is 3–5 weeks before departure. Booking too early can mean missing seat sales; too late means paying peak prices.

Shift your dates by a day or two: Saturdays are typically the cheapest day to fly this route. Avoiding Friday and Sunday departures can save significantly. September is historically the cheapest month on this route.

Weigh up connecting flights: Connecting flights on Seattle to Denver can be 20–40% cheaper than direct options. If you have time to spare, it's worth comparing.

Factor in baggage fees: Low-cost carriers on this route often advertise attractive base fares but charge separately for checked luggage. Always compare the all-in price — a $20 cheaper fare plus $50 baggage fee is no saving. Alaska Airlines and American Airlines may have different inclusions, so check each airline's fare conditions.

Search in private browsing: Some booking sites use cookies to track repeat searches and may show higher prices after multiple lookups. Use an incognito or private window — or just use Booked AI, which pulls live prices without any tracking markup.

The cheapest flights from Seattle to Denver start from $351, with typical prices ranging from $351 to $651.

The typical flight time from Seattle to Denver is approximately 7 hours and 8 minutes.

Airlines operating this route include Alaska Airlines, American Airlines, Hawaiian Airlines, Frontier Airlines.