Folding bikes like Bromptons ARE allowed as carry-ons!

[jlzpo1]

Just an FYI for those with Bromptons

I was able to take my folding Brompton bike on the airplane at different SWA locations including SFO, TUC, Orlando and PHX.

The problem you may face is at check-in or at the gate, where SWA reps may not be familiar with the bike, and may arbitrarily decide that you have to check it in as special cargo. 

Make no mistake, you don't have to do this.  If need be, copy this pic of my Brompton in the overhead bin  of a SWA flight from PHX to Orlando! The crew should be accomodating, like the ones on the flight I took. 

[LindseyD]

Thanks for posting, @jlzpo1. I'm sure this will come in handy for others flying with the same kind of bike. 

[jlzpo1]

This is why I prefer to fly SWA- you guys are friendly, reasonable, and use common sense to guide your decisions. It's more than I can say with any other American carrier. Thanks-

[wildthing]

Wow do I disagree! SWA is one of the most unfriendly for folding bikes I have ever taken!

I flew AlaskaAir to Portland from Oakland,they were nice, and checked in my folding bike as a free piece of luggage. Southwest however on the way back insisted on charging me $75 for oversized! Pulled out the tape measure and said it was a few inches over! Very NOT nice about it, and were insistent. DONT fly SWA if you have a choice, fly AlaskaAir. I tried customer relations and they refused to refund me the oversize charge. SWA customer service: NASTY!