We fly frequently with Toto on United. I use an airline approved Sherpa bag for Toto ... plenty of vents, etc. If this is Ranger's first flight, I would suggest that when you decide on the bag, set it somewhere handy for him and let him get used to it. I didn't make a big deal out of it, didn't put her in or anything, just let her smell and explore. I opened the top opening and just left it open ... put her favorite toy in the very back to make her have to go in there if she really wanted it! She did not want it
that badly.
The next day, I replaced the toy with her all time favorite treat ....
bingo!!! She stretched waayyyy in there and tried to reach it and finally, quick as a wink, zipped in there and grabbed it really fast! After that she crept in there and before I knew it she was napping in there ... piece of cake! We then took small trips out with her in the bag ... now, it's her favorite place! [sorry that was so long] I also learned [the hard way] that it's a very wise thing to have some emergency supplies ... small water bowl, a meal or two extra food and anything else she would require for a day or so. You never know, especially this time of year, when your flight may be delayed, re-routed or outright cancelled and you can be stranded for a day or two. We humans can pretty much manage for ourselves, but I can assure you, I have never found Yorkie food, etc. at any airport! Good luck flying with little Ranger ... hope some of this will help.