There is a new model called the baby case for screw bell bass trombone that looks to replace this case. Next Bonna case arrival is in January, we'll have info about it then.
This is a lightweight fiberglass case for bass trombones with a screw bell flare. The case is made in Brazil by Marcus Bonna, and fits a single or double valve bass trombone with a bell up to 9.5" (24cm) diameter. The outer cover is easily removed and replaced if it ever needs repair, cleaning, or replacement. The inside features modular foam blocks to customize the fit to your instrument. The 12x16" (30x40cm) music pocket attaches with zippers and is easily removable. The pocket features loops to hold a trombone stand. There is a small storage compartment in the small end of the case, and a small pouch in the middle that may hold extra leadpipes.
Though few of us have a trombone with a screw bell flare, those who do will find air travel to be very easy. This case would be welcome on most planes, and looks to be the size of a viola case. For rough travel we do recommend adding some extra padding inside so all parts are protected from each other. A few shirts or towels might do it. Though the shell is fiberglass, Mr. Bonna regards these cases as hand luggage. Your results when using baggage handling services may vary.
Most airlines have a carry on bag size limit of about 50 linear inches. This dimension is calculated by measuring all the way around the short sides of the case, plus the long side. If you measure in imperial, a 10x10x30" case would be 10+10+10+10+30=70". This case is over the carry on limit, but the TSA has exceptions for moderate size musical instruments, up to the size of a guitar.