OP, the problem is you're probably trying to book on AC or LH metal. If you can find availability on UA metal the surcharges/fees will be a fraction of what they are on AC/LH. There's a thread on which carriers to avoid. I'll let someone else find it.

Sadly, if you had UA miles, you could book on AC metal for roughly 1/10 of the cash cost that Aeroplan wants. AC has relabelled those fuel surcharges as carrier surcharges now that the cost of fuel has plummeted.

Welcome to FT.