Southwest Airlines is having yet another sale, so business must be bad. Hey, you already knew that. A 14-day advance purchase is required, travel is Jan 6 through Mar 12 (although probably peak travel during the February school vacation week will be higher).
Sale is not systemwide, but many routes are included (travel to/from both Orange County/John Wayne Airport/Santa Ana and Washington/Dulles is not included). Sale ends Dec 29 at midnight.
Fares range from $49 to $109 each way, no round-trip purchase required, Mon-Thu and Sat; $59 to $159 each way Fri/Sun. Other airlines will no doubt match or even beat these prices, as they often do.