After an evacuation was required on the Challenger lift at Big Sky a couple weeks ago, the decision was announced this week that Challenger will not run for the rest of the 2015-16 season. A planned replacement will be installed over the summer. Season pass holders and employees were notified by email. The news was available in local media outlets and Facebook on 2/15/19. Upper Challenger terrain can still be access via the Headwaters lift over at Moonlight.
For those unfamiliar with Challenger, some pics of the existing old double chair:
The other lift that will be replaced over the summer is the Lone Peak Triple that dates from 1973.
There is some discussion of the location of the planned lifts in the ongoing Big Sky thread.