When are flights to New York or Europe usually cheapest?

Depends. If your looking for a certain day in a month, Tuesdays and Wednesdays are the best. Fri Sat Sun are always big travel days, and often people return from weekend trips on Mondays. I don't know why Thursday is expensive, but with most airlines, it seems to be.

As for the month, August thru October is the cheapest. The months you want o avoid traveling in December and May. Everything else is relatively the same. I did the search for the third Wednesday of every month. Hope I helped

During the year like November.

I traveled to London, Paris, and Stockholm last November around Thanksgiving. For some reason, it seems cheaper to travel during late November

I'd say October, early November.

Summer time because alot of people travel in the summer. I hope I helped.

fall and spring