This is by no means meant to be information that always works but a number of my friends live the same life that I do and spend most of the year overseas. Most of these people don't have tight family relations and the traditional Western holidays like Christmas aren't very important in their lives. This doesn't mean they have a bad relationship with their families, they just have different priorities, much like my own does.
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It's no secret that airlines seriously jack the prices of flights during this time of year and they have no reason not to because the airline industry, just like any other industry, is a game of supply and demand. If they can get as much as they are charging for certain time-periods they will do exactly that. I have looked at prices on some flights not because I am going anywhere but because I was curious about how much the airlines were price gouging these days for the holidays, especially considering that global travel was still quite limited this time a year ago.
I found that round-trip flights that I would normally get for $600 are going for over $1500 ONE-WAY this December. I've seen some high prices in the past for certain days and since I don't really have a schedule it doesn't really apply to me anyway, but I do feel bad for the folks out there that don't have any other choice and only get a few days off of work.
There is one thing that I noticed at least about international travel out of the United States during Christmas and that is that certain flights can be obtained for LESS than what it would normally cost. While the airlines don't make any explanation as to why this is the case I think I have a theory about it. When the holidays hit, Americans all around the world feel a pressure to return to their families for the holidays and they will do so no matter what the cost is. However, certain airlines don't have a large enough fleet to continually stock these flights out of certain airports and they need the same plane that just flew to somewhere like New York City to return to where it came from. They will fly this plane that distance whether or not it has any customers on it at all and therefore you can get some pretty great deals on a near empty plane if you are fortunate enough to find an airline that is in this situation.
I have only one example, but it is a good one. A friend of mine who works and lives in Japan decided to dodge the inflated prices and traveled to USA in very early December instead of waiting until closer to Christmas when the prices get elevated a great deal. On the return trip he was able to score an economy class ticket that would normally cost around $800 for a mere $350.
Does this have to do with the fact that Japanese people don't celebrate Christmas with the same enthusiasm that Americans do? I don't know for sure, but it sure seems that way.
So if you do have a variable schedule like myself and my friend in Japan do, it could actually work to your advantage to pre-determine this one-way demand, and be on the cheap end of both of them. Travel agents can probably figure this out for you a lot easier than a website can, so it might be worth it to pay the few of them that still exist in the world to find this out for you.