Weirdest thing. I tried booking SFO-YUL using the Alaska site, but could not get it to work on this MacBook using Safari, Firefox, and Chrome. I could get a flight that priced out just a bit above the Porter site, but always got the error on all 3 browsers. Oddly I couldn't see the exact same availability as the Porter site as well. Tried to call AS reservations and they couldn't see the inventory. Try again a couple of hours later on my desktop PC. I'm able to see the same inventory and was able to book the flight at the Economy fare. Not sure if it was a fix on the AS end or using a PC though.