United Airlines offers several options for seat selection, and the availability of these options may vary depending on your fare class, MileagePlus status, and other factors. Here's a general overview of how seat selection works with United Airlines:

During Booking: When you book your flight with United Airlines, you will have the option to select your seats at that time. You can view the available seats and choose the ones that best suit your preferences, subject to any fees associated with seat selection.

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