I’m less worried about the fog messing with our Canada departure now than I was yesterday. Although they continue to cancel many flights, all the Air Canada flights to Halifax have been going each day. In fact, they’re mostly canceling domestic British Airways flights, with just a few short BA flights to other parts of Europe canceled.
The reason is because the fog doesn’t stop planes from taking off: it just reduces the frequency with which planes can do so. Normally, there’s a flight leaving Heathrow every 100 seconds or so. In bad visibility, that minimum time between planes increases. This means they can’t send out as many planes in a day; there’s just not enough time. So they cancel domestic flights, where people might have a chance of other arrangements via car or bus or train, but let the long-haul international departures take off.
So, all indications are that our flight tomorrow will take off on time, just like it has for the last couple of days.