When we book flights — usually months ahead of our travels — plans are often still unfolding. That was the case for a reader who asked about switching to an earlier Delta flight on the same day as her existing ticket. She holds a ticket to fly to Atlanta in the afternoon, but was enticed by a noon flight because an earlier arrival would mean more daylight for the drive to her final destination, Florida. Could she fly standby, she wondered.

It's complicated, in good and bad ways.

The good part: Anyone who wants an earlier flight can request a same-day flight change up to 24 hours prior to the departure time of his or her original flight. It's called "same-day confirmed," and it means that eager fliers could be heading to the airport assured there is room on their preferred flight.

The bad: As with most services offered by airlines, there's a fee for that. For all but Diamond, Platinum and Gold Medallion members, changing to a flight on the same day will cost you $50, whether via same-day confirmed or standby. Who wants to pay that, just for filling an otherwise empty seat?

Also, basic economy tickets (E class) are not eligible for any changes as of February.

Delta allows customers to fly standby only if the "same-day confirmed" option is not available. However, fliers can standby only for earlier flights, so they can get to their destination as originally planned if standby fails (again, there is an exception for elite members).

If you are going to try standby, you'll be happier if you do a few things. Call the airline to check on open seats. If hope prevails, arrive at the airport two hours ahead of the flight to be put on the standby list. Finally, pack light; you'll save no time if you arrive early but your luggage doesn't.

Send your questions or tips to travel editor Kerri Westenberg at travel@startribune.com, and follow her on twitter @kerriwestenberg.