There are two airports that you can fly into. Denver International Airport is the less expensive option. Transportation from DIA to Steamboat Springs takes 3-4 hours depending on type of transportation. There are taxi and bus services that run from DIA to Steamboat Springs, but need to be booked in advance. There are also car rentals at DIA if you want to be able to explore Steamboat Springs once you get here.
The Yampa Valley Regional Airport is located half an hour from the town of Steamboat Springs. There are taxi services that run to and from the airport and car rentals are also available at the airport. Uber and Lyft drivers service this area.