DTW allows people to enter the terminals without a ticket. However, you are required to apply to do so a day in advance: https://www.metroairport.com/about-dtw/

DTW allows people to enter the terminals without a ticket. However, you are required to apply to do so a day in advance: https://www.metroairport.com/about-dtw/dtw-destination-pass https://www.metroairport.com/about-dtw/dtw-destination-pass