The answer to this one is well stated above.
I fit everything in a 16" somsonite X-Space roll-on.
Don’t try it with a duffel bag without wheels, I tried it, the bag get heavy fast.
Most airport security knows scuba and usually it gets by with a cursory glance.
Just remember to remove knives (duh) and shares from you BC. And stow batteries
in checked bags. I don’t know what the battery thing is about, just something I read,
so I remove them from my dive lite.