Here's a video of a ride in a B-24. They seem to have let the passengers wander around at will while in the air except for take off and landing. I subscribe to this guy's scale modeling site and every once in a while he posts a video of a field trip like this.
This site says it is based in Massachusetts but I think the youtube video was shot while it was in California. Consolidated B-24J Liberator - The Collings Foundation
