I've only flown with my shield once. You definitely will have to check it. I used a 26" drum cymbal bag, and also wrapped towels around the edge of the shield and it was just fine. The cymbal bags do well to protect the front and back of the shield but if it's dropped hard enough on it's edge it could definitely get damaged.
Also I picked up another of the plastic Hasbro shields on Amazon today. I'll use it for cosplay and cosplay shields always get beat up so I bought it used on Amazon for $57 + tax with free shipping. I think it came to $61 and change out the door. Amazon has a number of used "cosmetic damage" shields starting at $57 and metal ones starting at $186. Probably not the route you'll want to go if you're just hanging it on the wall, but it's definitely a more affordable option for some.
Considering I tore the last one apart and painted it black, silver and copper I'm not worried about a couple of scratches.