There are space limitations for the ferry that takes you to the Arizona, so that's why you need a ticket for that. The Missouri is HUGE. You really don't understand how big until you see it. I can't see why they would ever need to impose timed tickets for it. I guess maybe the Bowfin could get crowded and they might make you wait as people clear out? But it's a pretty steady movement of people with the accompanying headsets that pretty much guide you along, so no one is lingering. FYI - we did the Bowfin in the morning first b/c it's right there, then headed over to the Missouri (they have a shuttle to get you there). We decided to wait for lunch until we got to the Missouri, and that was a huge mistake. Time it so you eat by the Bowfin. The Missouri basically has a food truck plus a snack stand, and a pretty small eating tent. The Bowfin eating area was far nicer. Also, the food truck line at the Missouri took me like 20min to get through, even though it was on the early side, barely 11:30, if that, standing in the full sun the entire time. Probably the most frustrating part of the entire day!