I took the Zephyr cross-country in 2021 and 2022, booked coach, and observation cars are definitely open to all. For the most popular sections (like through the

I took the Zephyr cross-country in 2021 and 2022, booked coach, and observation cars are definitely open to all. For the most popular sections (like through the rockies) there is a max capacity and they change out passengers every 30 minutes to let another wave of passengers see. Once it's not at capacity anyone can go, and stay as long as they like.