I am planning to take a Utah tour in May that starts Monday morning from Grand Junction, Colorado. It sounds both more exciting and more economical to fly to Denver (from Boston) Saturday and take the California Zephyr across Colorado on Sunday - the Boston to Grand Junction flight via Denver is much more expensive than the flight to Denver plus the Amtrak ticket and I would be taking the extra travel day in any case.
I am concerned about how likely the Zephyr is to be significantly late (say, more than three hours from its scheduled 5:30 Grand Junction arrival).
In a pinch I could rent a car in Denver and drive across Colorado (four people in the car, which would defray the cost). But thinking ahead to that possibility suggests I wait to buy my Zephyr ticket until the day before. Is the train likely to be full?