"What’s allowed?" I asked. "Saline solution, or bottles labeled saline solution?"
"Bottles labeled saline solution. They won’t check what’s in it, trust me."
They did not check. As we gathered our belongings, Schneier held up the bottle and said to the nearest security officer, "This is okay, right?" "Yep," the officer said. "Just have to put it in the tray."
"Maybe if you lit it on fire, he’d pay attention," I said, risking arrest for making a joke at airport security. (Later, Schneier would carry two bottles labeled saline solution—24 ounces in total—through security. An officer asked him why he needed two bottles. "Two eyes," he said. He was allowed to keep the bottles.) - The Atlantic
I highly recommend reading this article. It points out the ridiculous nature of airport security. Bruce Schneier really knows his stuff.