I flew towards the end of September, very late season but it was really fun! It was unfortunately a very gusty day in the valley, so we had a fair amount of bumps(which you really notice in a smaller plane) which caused another passenger to get sick. Fortunately, they carry motion sick bags and things to clean up.
The actual landing on the glacier was super smooth and it was calm inside. So glad these were still offered while I was there. Highly recommend!