Travelers to Europe, Asia, Far East, Australia, etc. should be aware of the fact that there are flight seasons: high or peak, shoulder or medium and low or off peak. High season would bring you the highest flight airfares and you can pay the lowest prices if you travel during the low season months.
The best time to travel to North Europe might be summer (June through August) or shoulder season for Southern European countries (Fall or Spring months). How to save money and get great flight deals during the high travel season? Here are some options. If you want to fly in summer, you may start looking for airfare 6 or more months before the departure date. During that time, you will be able to find seats (almost guaranteed) whenever you want. You will pay, however, a regular high season rate.
If you want to save money, you need to wait until a month or so before the high season starts (usually beginning of June; check with airlines to get the exact date). Airlines start offering flight deals and sales right before the season start. This also applies to shoulder and low seasons. Advantage is that you may save as much as a third of regular ticket price. But the drawback is that availability may not be as great as six months ago. If you are willing to take a chance and find lower prices on airline tickets to Europe, you must be willing to change the dates and be flexible, if necessary. Lower airfares mean fewer seats available for the lowest price and greater chance of selling out. So when you see the prices go up, it does not necessarily mean that an airline increased the price, it may well mean that the lowest price got sold out and then the next higher airfare is your new lowest price.
The flight booking systems in the US and in Europe slightly differ. You may easily find last minute cheap Airline Tickets to Las Vegas, New York, Los Angeles or other US cities. But last minute deals may not work for the European destinations. So research your destinations well before you travel.