Am in early stages of planning a trip to Yellowstone in Sept or Oct. Coming from East Coast, which airport should we fly into? We just want to do the more popular routes in the park...any thoughts?

I've never been in Sept. or Oct. but I do know that many of the facilities will be closing during that time of the year.

http://www.nps.gov/yell/cal.htm#Sep

You can learn more about the weather conditions here:

http://www.nps.gov/yell/planvisit/or...ther/index.htm

Is it possible to go earlier than September? If not, then I would plan as early in September as you can.

Utahtea

Ooops, I forgot to ask how long were you planning on this visit?

Utahtea

Following up on utahtea's comments, early September is a good time to go. The weather is still manageable, the crowds are down and the foliage is beautiful. By mid-September, many facilities start closing down...and the weather starts to get very cool at night. (Our flight was delayed by a snowstorm for five hours on a September 10!)

My family did Yellowstone/Grand Tetons last year and flew into Salt Lake City.

I think flying into Jackson, WY airport is best. The town is cute, the airport surrounded by mountains. It's an easy trip into town for lunch or a night, and then onto Tetons - or past the Tetons and onto Yellowstone, depending on your timeframe.

I'd book two nights at Old Faithful Inn or area if possible. From there you could go north to Mammoth for a night, then down to Lake Yellowstone. It's kind of a circle and you get a taste of various parts of this very diverse park. If you look at a park map, you'll see you can stop at Obsidian Cliffs, Grand Canyon of Yellowstone, etc. along the way. Also, folks at this site can answer specifice Yellowstone questions:
http://www.yellowstone-natl-park.com/wwwboard/chat2.htm

Bozeman is only about 45 minutes from Yellowstone and has a wonderful airport.