I was of the posters that originally compared PD and AC (I think)... and I also happened to be on PD on Thursday night flying YOW-YYZ (not YTZ).

I guess the downtown core was completely fogged in for much of the day and the entire evening or night. This happens to Porter 2-3 times a year. That is one of the downsides of the island, when they have weather issues, they are hit particularly hard.

I suspect the ended up with planes at Pearson overnight and that lead to delays the following day.

I believe this is the first time they've been severely fogged in with their increased schedule, and needless to say the handling was mediocre at best. They did recognize that fact in a form email sent out yesterday apologizing to all those that were inconvenienced.

I've flown porter YTZ-YOW in the morning 10 times so far this year, and everyone of those flights has arrived on-time (to the minute) or early. I've probably flown an equal number on AC, and technically they wouldn't landed on-time just about ever day too (there were probably a few de-icing days at the start of the year, but I'll discount those), but for AC on-time is within 15 minutes of the scheduled time.

Also of note, I gave up on Westjet, on this route primarily because they didn't have a lounge, but also because they were the least consistent of the 3 as far as on-time performance (in my limited sampling).