Talkeetna has the major flight-seeing business for cruise ship passengers who want to fly around Mt. McKinley and land on a glacier. They arrive by train or on tour buses from their cruise line's private lodges in the Cantwell-Healy area. It is also the departure and supply point for all the climbers who want to try their luck at ascending the highest mountain in North America. So, you have a choice of a single-engine Cessna, a radial Beaver, a turboprop Otter, a helicopter, or a pressurized twin that can fly over the mountain and not just around it. Lots of choices, many different per person fares.
My impression 15 years ago was when we did a flight-seeing trip that Talkeetna had become one of the busiest airports in Alaska when cruise lines began booking most of the flights and that was confirmed when we just visited Talkeetna again in 2013. By contrast, when I flew out of there on a job in the early 1970's, dogs were sleeping in the streets when we headed for the airport at the crack of dawn and it had the least busy paved runway long enough to handle C-130's anywhere in Alaska!
So, to make a long story longer, take PA12's advice and, if possible, fly from one of the other nearby airfields or from Fairbanks. And don't book a flight too far in advance--if you can't see the mountain, you have just wasted a lot of money.