One reason aviation interests so many people is because it involves so many different aspects that almost anyone can find some part they like. Since this is a STEM presentation make sure you hit each of those areas in a different way so you appeal to a larger portion of the audience.

Science: principles of flight, weather, how flying affects the body
Technology: modern cockpits, electronic charts, dispatch tracking tech
Engineering: there's some videos on you tube of 777 wing stress tests
Math: descent planning, lat/long

Good luck and have fun!