People investing in futures do this every day, and some of them are most certainly credible.
If it were possible to do significantly better than blind luck in speculation about future prices then there'd be nobody around to take the other side of the contract.
Speculators usually earn a premium over what they would get via blind luck. If they didn't, there would be no speculators.
The reason why trades occur at all is that not everyone is a pure trader. Hedgers (e.g. Southwest) trade futures to reduce business risk rather than to make money. They tend to make a net loss on trading but earn back a greater amount of money via their core business.
If it were possible to do significantly better than blind luck in speculation about future prices then there'd be nobody around to take the other side of the contract.