Q. My daughter has been hospitalized and will not be able to fly with her sister and I. What happens at the airport when we have three seats and only two of us checked in?  If they give our seat to another passenger will they give me a voucher? If we do not get a voucher, can I insist on keeping the seat empty and having more room for us? Our tickets were paid with Amex points and cash.

A. Sorry to hear about your daughter's illness. Hope she's better soon. Any chance you bought travel insurance for her?

If not, depending on the airline, they'll either give her a credit minus a change fee (up to $150 on a domestic non-refundable ticket) or give her the full amount in a credit. Southwest, for example, doesn't charge a change fee and your daughter can use the credit for up to a year.  But on another airline, the change fee might eat up most or all of the credit.

If your daughter doesn't check in for the flight, they'll probably give the seat away to a standby or other passenger. If you want to keep the seat empty, check your daughter in for the flight online and get a boarding pass at a kiosk. That way it's unlikely anyone else will claim the seat, although if a flight attendant or other employee notices the seat is empty and the flight is oversold, the airline may still attempt to claim it.