The youngest I travelled with my son was at 3 months but I did the stroller combo you have (Evenflo pivot extend) and we didn’t have trouble traveling through the airport with it. My only worry with the uppababy would be to get something so expensive get damaged. Maybe look and see if they have a travel bag?
We have the same stroller carseat combo, and travel very frequently. We decided to purchase a carseat specifically for traveling so it's ok if it gets ruined. And our travel stroller is the Zoe. I can't say enough good things about it!! Reclines almost flat, very large sun shade, decent storage underneath, and suuuuuper lightweight. If you want to keep your babe in their Mesa seat I'd maybe look into getting the uppqbaby minu stroller for your travel stroller? You can always bring the carseat on board if you purchased a ticket for your babe, or even gate check it - just get the travel bag for it. I personally like having two strollers, plus they're great quality and will last you in the years to come so it could be a good investment.
The minu you could also gate check .... orrrrr I'm pretty sure it's one of the ones that fits in the overhead compartment.
Following because I’m curious too