Dreaming about a plane crash is a relatively common thing. Plane crashes are horrific news stories and they help represent a loss of control.
Planes are normal means of transportation, but they move thousands of feet up in the sky. Unlike a car or train, if a plane has a problem you can't just stop or hope you run into something soft. You are completely helpless and in the hands of the pilots up front, who may or may not be able to fix whatever is wrong.
For you to dream about a plane crash means that something OUT of your control, that you should be able to rely on and trust in, has gone haywire. This isn't about you and something you should have been able to do properly. This is about someone or something else that you *Trusted* that let you down completely, in a way that had a huge impact on your life.
Plane wrecks aren't about small dings that a mechanic has to fix. Plane wrecks are about huge national-news issues that affect many people.
What major incident in your life is causing you trouble? What large issue, that should be reliable, has gone off kilter?