Before you do anything, what is the cost of the other ticket? If it is lower than what you paid AC, you are entitled to a full refund of your AC ticket and can then purchase the PAL ticket and save some money. You will be carrying two tickets on your credit card until the AC refund posts, but that may be an easy solution.

As it stands, your flight has remained on a 2:40 delay for over 3-1/2 hours, so the AC flight may well go.