We do not have enough data on this route to provide a reliable graph showing how many days before departure it is the best to book.
However, usually the closer it is to the departure, the more expensive the tickets are.
The most popular airlines on the route Chicago O'Hare - Seattle Tacoma: Alaska Airlines (AS), Frontier Airlines (F9), Spirit Airlines (NK).
Direct flights last about 4h 32min.
Direct flights available 3 days a week - Monday, Tuesday, Saturday.
Direct flights: Alaska Airlines (AS), American Airlines (AA), Frontier Airlines (F9).
Chicago (IL) Seattle (WA)