Protec IP-306CT Tenor Trombone

This bag fits easily into the overhead locker on a plane. I use the back-pack straps (sold separately) and have never had an issue with any airlines carrying this on as hand luggage.
I am a bit disappointed with the mechanism for holding the bell in place. It isn't great and it moves around a bit. I usually pack a spare t-shirt in there anyway which helps, but if you're throwing this around in the back of a van then it's not the case for you.

I bought this bag about a year ago for my Tenor Trombone and have been very happy with it. It has multiple soft paddings that can be fitted to better fit your trombone, and the front pocket is great for sheet music, pencils and other supplies. The lid is a bit top heavy, so the case will usually tip when opening the case but it isn't a big deal for me. Overall great purchase.
I also bought the straps but haven't really used them that much. They are fine for when you're travelling, but are a bit flimsy, and are not necessary.