Traditional Taxi Cabs 

Seattle Yellow Cab operates the Taxi stands at SeaTac airport with Taxis and 8-10 passenger vans available 24 hours a day. No reservations are necessary. Cab fare from Sea-Tac International Airport to downtown Seattle runs $42-50 one-way. For a map to the Seatac taxi stands visit this link.  Once downtown you can take your pick of cab companies. Taxis, unlike TNCs, allow you to pre-book rides. These days the best way to get a Taxi is to use a Taxi booking app like Seattle Yellow Cab'sOrange's or Flywheel.  While cabs are metered from the airport to downtown, cabs charge a flat fee (currently $40) from the downtown hotel zone to Sea-Tac Airport. STILA is the on site limo and town car provider at Sea-Tac established by the Port of Seattle. Since they charge fixed rates, the amount for a limo into Seattle can be as cheap as a cab, but not always.  Town cars and limos from the airport are available by calling #55 from the phone near the hotel ads in baggage claim. The current rates are $45 for a town car.

Links: 

Farwest Taxi 

Orange Cab

Seattle Yellow Cab 

Sea-Tac Airport Ground Transportation 

 

Transportation Network Operators (e.g. Uber or Lyft)

New app-based "ride-hailing" services UberX & Lyft and Wingz are of of 3-31-2016 are now allowed to  pick up passenegrs at SeaTac.  They are still prohibited from picking up on the airport drives, however Seatac has a pick up area in the parking garage next to where the cab line is.  Just cross the skybridge from Baggage Claim and you will see the signs.  UberBlack does offer flat rates, with no tipping from the airport to downtown Seattle at $55 for a towncar. Within the city of Seattle, rides via UberX are less expensive than traditional cabs unless they are surge pricing. Unlike traditional Taxis that have regulated rates, Uber and Lyft can change prices at any time. UberX & Lyft also do not allow you to pre-book a ride. Uber offers several levels of service, which "UberX" being the least expensive. There is no expectation of tip and your credit card is charged through the app. More information here:  Uber Ride Hailing App  

The same is true for Lyft, although their app does not provide an estimate of how much the fare would be. Within the city a ride should be less than a taxi unless they are "Prime Time" surge pricing. As with Uber, there is no expectation of tip and your credit card is charged through the app. More information here:  Lyft Ride Hailing App 

Both Uber and Lyft are available for trips anywhere in the city and in practice will result in a car picking you up with 15 minutes in most places.

 

"Flat Rate" For-Hires

Seattle has "For-Hire" vehicies that look like Taxis but are not and by law cannot call themselves a Taxi, Cab or a Taxicab. Seattle offers a flat rate based on zip code that is not metered by time or mileage. You must pre-book these trips. They currently offer a rate from downtown to Sea-Tac for $29,  . This company offers ride in the city, as well as to and from the airport. One of the largest of these firms is Flat Rate for Hire. They have 400 cars which cover the Seattle metro area.  You just call or text them when you need a ride, but they are not allowed to pick up ad hoc fares inside the City of Seattle.

There is a tool for estimating fares available online, which gives you the ability to compare fares.  The site lets you plug in an origin and destination, then comes up with a fare which doesn't include any airport fees. In general the for hire vehicles almost always are cheaper than a metered cab. The advantages multiply if you arrive in rush hour or during heavy traffic. Wait time in cabs are charged at $.50 a minute, whereas for hire vehicles are always a flat rate.

The ''official' airport taxi fare estimator shows an average fare from Sea-Tac to downtown Seattle at $52.50 making the fixed rate STILA limos a great value. 

You can check them out here:  http://flatrateforhire.com/