Oh dear, seems as though your having Deja vu dreams. I also had those, but not really disasters and accidents. I did some deep research about it, all the while thinking I was someone special like a psychic or an assuming prophet. But no, it happens to a lot of people. They talk alot about it over the internet, and they say its just pure coincidence. Although it can't be explained by science, we should net fret over it. This is normal and we should keep it that way. Weird things happen everyday, that includes dreams. Dreaming about crash incidents and thinking that there is a slight chance that it might happen sure is unnerving though. I advice that you should tell someone close about it, just to let it off your chest. Also going to a therapist helps. Were here if you need more advise about it. Hope you get through this.