What type of glue should I use to assemble balsa wood models?

It's not really about the type of glue, more about what you're actually building 😅 For balsa in general, regular white glue (like Elmer's or the equivalent) works fine for light stuff, but honestly wood glue like Titebond is more solid and dries fast. If it's model planes or things that move around a lot, you've also got cyanoacrylate glues (super glue) that do the job in two seconds. Balsa is fragile so you can't push too hard with big joints - a thin coat is enough.