I flew Allegiant with Bonnie in August of last year. Going to Orlando from GSP they didn't even check her bag at all or ask for her vet records. But when we flew home out of Sanford they did check her bag and ask for her records. On the flight down the attendant told me I could take her out, but on the return flight the attendant was a biotch and I don't think she liked dogs (or people for that matter
) That is the exact same experience we had with Delta when we flew to Oregon a few years ago...the attendant on the first flight was very nice and let me take her out, but on the return flight they didn't!
All in all I would say flying Allegiant with a pet was a good experience. We will definitely do it again.