I’m 100k but have never used the same day flexibility benefits. Old forum posts seems to suggest you could pay a fee as a non elite to make a same day change and that the fee is waived for elites. But when I view the current frontier website I can’t find any mention of any sort of same day confirmed change policy except that you can make a change and pay the difference in fare?

There is mention of same day standby for flights earlier or later. Can this be done on the phone or website or social media in advance or can it only be done at the airport? If I try to standby for a later flight what happens if there ends up not being seats that day?