There's an old saying that an airplane doesn't make money sitting on the ground. That's why airlines do everything they can to keep planes in the air on as many as flights as they can. For example, if they can cut the turnaround time between flights throughout the day, then they can probably add an extra flight at the end of that day. But once we get into the late-night hours, things change.

Simply because of the lengthy travel and numerous time zone changes, overnight flights are routine for long-haul distances. But not many people want to fly at night for domestic or regional travel. It used to be that airlines would run a ton of domestic overnight flights; fuel was cheap, so if you could cover that and the cost of the crew, then you could make money. America West even had a night-flight hub in Vegas, but when fuel prices started to spike, the cost of running those flights jumped while demand failed to keep pace. The hub was dismantled and many other airlines cut their marginal red-eyes as well.

Airlines also use the wee small hours to perform aircraft maintenance, but of course not all airplanes that sit overnight need work. So airlines have had to get creative in order to increase their aircraft utilization when you're sleeping. The key is to find markets that can be profitable even during those late-night hours. That has become much harder with higher fuel prices, but clearly airlines are still finding a way. Here's what they're trying:

Going Cheap
Spirit is known for barebones customer service, no frills, and extremely cheap fares. But to keep those fares low, it has to run its airplanes more frequently than most. That has resulted in some pretty hairy red-eyes, including the brutal Phoenix to Dallas–Ft. Worth. flight leaves at 1:55 a.m. and gets into Dallas at 5:05 a.m. (It leaves an hour earlier once daylight saving shifts, since Arizona doesn't change.) It regularly clocks in at about one hour and 45 minutes in the air—good luck getting any sleep on that one. But if people want cheap flights, they'll put up with the pain.

Following the Family
JetBlue is known for great service, great legroom, and live television, but it is also earning a reputation as a great way for Caribbean families to travel back and forth between their homes in the northeast U.S. and their relatives in the islands. For example, JetBlue is increasing its service this summer to include eight daily flights from JFK to both Santiago and Santo Domingo in the Dominican Republic. It's effectively a 24-hour operation with flights arriving at 12:50 a.m., 2:15 a.m., and 3:30 a.m. with similarly painful departure times. Why would such customer-unfriendly options exist? Because seeing family is most important and that means flying whenever you can get a more affordable fare.

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Venturing North
Another summer trend centers around Alaska. JetBlue started Long Beach to Anchorage a few years ago and will add Seattle to Anchorage this year. Virgin America will begin San Francisco to Anchorage this summer, and Southwest has also expressed an interest. Why are airlines so interested in the 49th state?
Demand to Alaska explodes during the summer, and fares are high. So airlines can add flights there and still make good money. What's more, people generally expect to fly at night in this market. There's nothing quite like leaving the Continental U.S. when the sun is shining, seeing the sun set, and then seeing it un-set as you reach Alaska and its 24-hour daylight. And by incorporating red-eyes, the airlines can use airplanes that would otherwise be sitting still.

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