Imagine that you and your family have plane tickets to go to another country. All the plans have been carefully considered and taking care of. If you missed this flight, you won't be able to go until next week and then whatever plans you made abroad will be ruined.
You reach the airport with your family and just before it is time to board the plane, a woman who looks pretty average to you starts talking very loud and announces she is a psychic and last night she had a dream about this particular flight. She claims the plane will crash and all the passengers will die. She is begging everyone to NOT board the plane.
What would you do? You only have few seconds to decide.
I would not get on the plane. I think that if someone is making a big fuss about it then something could be wrong. I would go back and try to recoup some of the money I spent. Most trips that I do plan are open for change just in case. I would see what I could do with the airlines but I would rather my plans change then get on the plane.
There are so many nutcases around that unless the person was a noted psychic then I would not pay it much heed.
I understand Harkon's view however if the person was sent as a warning to you and you ignore it then you have essentially booted 'help'.
The person could be psychic, insane, or they could just know that the pilot is drunk. If someone was freaking out about the plane, then I'm sure there would be a major inspection of the plane. The flight would be delayed, and future would have changed to where there probably wouldn't be any crash. I would probably wait til the next day to take that flight though, and I'm sure the airline would refund or exchange those tickets due to the chaos.