There's three main airports that you can fly to depending on how far you want to drive when landing:

Denver Airport (DIA) is 4 hours away, but the cheapest option. You can rent a car, or you can take the light rail (which leaves the airport every 15 minutes) to Union Station. From there you can take a bus to Crested Butte. (https://ridebustang.com/outrider/schedules/crested-butte-denver/)

Montrose Airport (MTJ) is an hour and a half away from Crested Butte. United, American, Delta, and Southwest all have a couple flights a day into Montrose.

Gunnison Airport is the closest (30 mins from Crested Butte) but flights tend to be more expensive. May be worth it depending on when you are flying in!

We've reserved the front unit in the Mule Barn (709 Maroon Ave.), as well as a VRBO one block over (707 Gothic Rd.) that can house everyone at the wedding. All units are available 8/19-8/23. If you are not looking for a shared space for this trip, we'd recommend Purple Mountain Bed and Breakfast or Cristiana Guesthaus (these are super close to the Mule Barn).