We ask your opinion: 

Flight POE134 originated in Newark, leaving at 9:11 on May 5.  Plenty of time to reach CYTZ -- however its trail on flightstats and flightaware, veered off towards Peterborough (there is a municipal airport there, we think) and it circled there (3 times we see -- see link) until it was too late to land at YTZ.  Thus diverted to Pearson.

http://flightaware.com/live/flight/POE134/history/20100506/0040Z/KEWR/CYYZ

We noticed the weather that evening was somewhat foggy as we are near the Island Airport and still heard the whine of aircraft.  We didn't think the weather was a factor that evening, as we have seen worse, but it could have been. 

In your experience, we ask: 

1.    if weather is an issue, has the Tower said, weather is an issue, you must divert?

2.    do pilots decide if weather is an issue and cannot risk landing, so they ask to go to Pearson? 

3.    who would decide and why, in particular, to circle around Peterborough? Would this be because Pearson was too busy to accept a Porter flight, so wait until we call you?  Is this why it circled around land instead of circling around water?  Or is that too dangerous to do?

4.    We have noticed that if a Porter flight is very late it sometimes diverted to Hamilton. Why is that?  Does Hamilton have no curfew?

Thank you.

Skywatcher