They is no humor intended. Not sure why this was moved. I am serious. You can wear 3 pair of pants and 6 shirts, why not a helmet.
Do you really want to give any agent of any type of security agency in a mass transit (target rich) environment ANY reason to be suspicious or nervous? In today's security environment? That crosses the line from cognitive dissonance to willfully and intentionally dense. Just looking for trouble. Next you'll say it's a full face helmet....
Put yourself in the position of the guy/gal on the other side of the aisle. You're TSA or any of the other several agencies that regularly patrol an airport. Out of all the people on a concours or in a gate area there's one who just has to wear what might easily be perceived as protective gear. What are you going to think? And if you think they would be "professional" enough to consider and dismiss you how about all the civilians who aren't regular flyers, who are already moderately wound up just because they are flying, and they see someone wandering around with a helmet on?
I'm use to airports. I've got no insecurities about flying. I'm unfortunately too familiar with people of questionable judgment (how was that for politically correct?

). I know what a motorcycle helmet is. And even I don't want to suddenly see some dude walking along in airport traffic with a helmet on. Not in today's world.
Just stick the lid in a backpack or other carry on. Fill its interior space with socks and shorts. Don't look for reason to draw attention to yourself and make others worry. If you're going to wear the lid in the airport anyway, y'know, just to prove a point, you might as well get stickers for it that read "bomb" and
"Putin khochet chtoby vy vse umerli!"