Deviation from plotted route

[BDarlin]

I am a total newbie and tracking my daughter’s flight from Hong Kong to Toronto. I notice that her Cathay Pacific #826 is deviating quite a bit from the planned route shown on the Flight Tracker.

What is the reason for this? Her flight to Hong Kong a few weeks ago was pretty much exact for the projected route displayed.

[cbw]

Not sure why it hooked a left there. Estimated positions should follow a great circle path from the last known position. I just checked the flight and it appears it is on the correct path currently.