The VistaVision cameas used by ILM used 35mm, but ran it sideways so that on frame was exposed over what would normally be 2. In effect it gives the resolution of 70mm without having to use the more expensive 70mm film stock. Everything was then composited onto 35mm film to create the master negative.
Very few movies have been shot on 70mm film. But distributing on 70mm eliminated the increased grain that distributing on 35mm creates.