This video shows in detail how my Brompton bicycle suitcase travel trailer works. None of the commercial options met my requirements, so I made my own.

The system is centered around a tough, airline-sized ABS suitcase. Since I made it years ago, I've flown with it and taken it onboard trains many times, and ridden it as a trailer for many miles. Not once did my beloved Brompton or the stuff I had packed inside the suitcase alongside it get damaged. The suitcase itself has taken a beating over the years though, proving it's an effective shield against the brutality of airport baggage handlers.