If you want cheap(ish) flights for xmas make sure your departure date is no later than 8th December as after that date they shoot up because it is then "Peak Season".
I always make sure to fly out on the 8th and always manage to get flights at just over £500 (economy) Return flights may be a bit more of a problem if you leave it too late before booking as most people fly home around the 5th or 6th. Last time I couldn't get a return flight before the 16th January, so had to stay in LOS longer. Bugger !!
