A few years ago I was to pick up a colleague flying into YYZ from YOW on Westjet, but they shut down all the flights due to a snow storm. AC, however, continued to fly. So my colleague rebooked on AC and arrived about an hour late. I don't believe he ever did get an answer on why AC could fly and WS couldn't. Other airlines were also flying into and out of YYZ using a variety of equipment, so I doubt it was a mechanical limitation. I'm at a loss. Union issue? Are WS pilots unionized?