A full bladder is...
an emergency except to USA air carrier cabin crews.
When they tell you "sit down", you are supposed to "sit down".
Ein, zwei...! - If not, you are a (full bladder) terrorist.
No matter what. No barking, and pee in your pants.
I would recommend one of these flasks (Paul Masson) with large bottleneck.
Obviously, you will then be arrested upon landing for "indecent exposure".
xxx
You see, I was born in Europe, and now live in South America.
When I have a full bladder, "seat belt sign ON", I go. There, they understand.
They guess "you got to go"...
xxx
When I am on the road, with my car, I stop next to the nearest tree.
Or walking in whatever village or town, a wall, if available.
If windy, I have my own wind sock to aim properly, avoid the shoes.
Ladies seem to generally prefer doing it "behind the car"...
Try that in USA... (I lived 25 years near Los Angeles).
xxx
Happy contrails