there's a reason that nobody goes there.  Aniakchak has horrendously bad weather, and with the caldera being 10 km wide, it generates its own weather.  a third of the people that visited in 2011 had to be rescued by USCG.  the best time to go is in august, when the storms aren't as bad.  bring a whitewater boat and ride down the Aniakchak river to the bay.  you can then follow the coastline to chignik and fly out.  if you rely on aircraft picking you up inside the caldera, and the weather socks in, you may be stranded for weeks.