1st off as a Aircraft Mechanic for Southwest Airlines for 23 years I appreciate those who have chosen to fly on my birds, thank you very much.
My biggest piece of advice is to pay attention to your surroundings, at Dallas Love Field a checked firearm goes behind the counter for TSA inspection, stick around for 30-45 minutes before actually going through the metal/small pee pee scanner, in Corpus Christie the TSA is right there at the ticket counter and you know immediately if your firearm is going to make it for the ramper to load in the belly. 99%, I use non TSA locks, YMMV.
Also the air on all commercial airliners up to 50% is recirculated, this is done to boost efficiency, but the only air that is actually recirculated is from the forward bag bin and electronics bay where the air is used for cooling various components , and it goes through a HEPA filter before being reintroduced in the cabin, then its vented overboard, unlike your car/truck we change filters when Boeing/Airbus says to.