Be sure to followup with Merriam-Webster, Cambridge & the Oxford English dictionaries about how you'd like them to redefine "firm".

I like PD for my YTZ-EWR flights. I now fly up on JJ (if the flight operates on that day) JFK-YYZ and then YTZ-EWR on PD as PD offers complimentary same-day changes on the YTZ-EWR route. Who knows when a client meeting will run late or I'll want a few hours more with friends that weekend.

I do wish they still offered 1 free roll-aboard or checked bag like they used to though. But instead I buy the fare that includes it.