>when is the best time to fly?
I suspect that's pretty hard to answer and depends on where you are and where you want to go.
My own personal experience traveling mostly US to/from Europe would indicate that in general spring and fall are much better than Summer, and winter is the least expensive time. Holidays, like Christmas, can be extra good if you fly on the actual holiday, like Dec 25.
But there are lots of exceptions that might be hard to predict, like a large trade show in a particular city, such as Las Vegas or Chicago in the US, or in many European countries, like the Hannover Fair in Germany or Mobile World Congress in Barcelona, etc. Too many to list.
In Asia, I know that there is "Golden Week" in Japan in May, which travel-wise is not unlike Thanksgiving in the US. But as in the US, travel is busy only at the start and end of the holiday, and often less busy during the holiday when everyone is already where they were going.
As for me, anytime is a good time to travel!
