On Monday, I flew two Continental flights, gate checking the Brompton for both of them. In short, I encountered no problems.

The security at O'hare was pretty uncurious about the whole thing, and merely scanned the bike and waved me through with the usual bored line-clearing attitude. Continental took the bike and gave me a gate check ticket, again without a fuss (pictures included). This was a crowded commuter flight between O'hare and Newark, sold out. I don't know of a better way to stress test the US domestic flight system.

When I got to Newark I had three hours to connect and was feeling antsy. My bike was next to the strollers this time, rather than in baggage claim, probably because of the connecting flight. I decided another run through security was worth the exercise and went off to ride the Brompton around the parking lot for a half hour or so.

On the way back through security I encountered trouble! Turns out I had forgotten to empty my water bottle, which the helpful TSA folks proceeded to do for me. They also developed somewhat of an interest in my pepper mill, but gave it back once it was determined to have pepper in it. The bike? Not even glanced at, other than by the X-ray technician, whose job it is to look at things.

The connecting flight to a regional airport went smoothly also. In this case I had to gate-check my T-bag as well into the underbelly of the small turbo-prop plane: I experienced my first pang of worry watching my laptop get loaded onto a conveyor belt! Needless to say, my Brompton and luggage were waiting for me, unharmed, when I arrived at my destination.

My conclusion, after three security clearances and three gate checks: this isn't luck, this is just how the airlines deal with a small piece of sporting equipment that they don't recognize. If it fits on the conveyor and isn't prohibited, it's allowed, and if you give it to the gate attendant, he or she will check it for you without complaint.

I admit I was nervous to try this on Continental, which is now United. But each person in the intricate airline operation has their job. It's the purpose of TSA to find bombs, not exclude bicycles, while it is the purpose of the gate attendant to get everyone smoothly off and on the plane. The check-in crew is there to make sure you obey baggage regulations and pay all the extras the airline wants to charge; I avoid them whenever possible, especially with something weird like a folding bike.

Basically, I haven't encountered any trouble, but if I do, I will refer to my bike as 'sporting equipment' and expect everything to be fine. I hope to continue to update this thread from time to time with travel stories; flying with the Brompton has changed my entire travel dynamic, and I'm going to keep doing it.