If you can't speak up without being fired then you need to find like minded individuals and tank the company. Sure, you'll probably be fired at some point but you can do lasting damage first. Nothing crazy of course. Just the little things that make a big difference. Every large Corp has plenty of room for you to gum up the works for a long time before being fired.

If you're a pilot, make the flight uncomfortable for the passengers through turbulence, rough landings, climate control, delays, etc.