In less than three weeks, the Pittsburgh International Airport will be crowded with college kids bound for spring break. They will flock here in scarves and parkas, which they will shed on their way to places warm and exotic. Airline clerks will tend to the ticket lines that snake around the lobby, baggage claim klaxons will blare, and thousands of travelers will empty the change from their pockets and hurry, single file, under the metal detectors.

For now, though, at 2 a.m. on a chilly February morning, the airport is all but empty.

Of the over 600 flights that depart here daily, not one of them leaves between 12 a.m. and sunrise. This is the graveyard shift, the time of day when newsstands are closed and terminals abandoned. A single vendor, Treat Street Concessions, remains open, brightly lit by heat lamps and fluorescent bulbs, but its lone staffer says that no one buys anything from him at such a late hour. “Not that anyone buys anything here during the day, either,” he jokes.

But though these early morning hours are the quietest of all, they also might be the most important.

The baggage conveyor is motionless now, but its hum is replaced by the steady whirr of a lone vacuum cleaner. The elevator is stopped, but a maintenance man is putting it in order, tinkering with its glittering metal control panel. While the rest of the city sleeps, the night crew here is working to keep the airport a well-oiled machine. Although they amount to less than 2 percent of the airport’s 20,000 employees, these are the people that spend the pre-dawn hours doing all the cleaning, maintenance, and preparation for the coming day, the essential legwork that is often forgotten once the sun is up.

The cleaning crew is out in full force at this hour, sanitizing bathrooms, polishing escalator rails, and mopping walkways. Shawn Yaros, a 25-year-old employee of Multi-Purpose Cleaning Company, pushes his yellow custodial cart across the vacant lobby, stopping now and then to collect debris or wipe smudges from glass. He has worked the late shift for six years now — 11 p.m. to 7 a.m., five days a week — and says that it has definite pros and cons.

“We all know each other,” he says of his coworkers. “It’s slow-paced enough so that we can talk and have fun, so we don’t really mind it. But I don’t think you ever really get used to some things about graveyard.”

Stan Fancher, Yaros’s coworker, agrees. Fancher, 53, has spent time in the military and has also worked as a night shift postal worker, so he is no stranger to long, late hours. But though he says his body is accustomed to the erratic schedule he keeps, he still finds it difficult to overcome the time he loses with friends and family. Fancher’s wife Vanessa works by daylight at the Kane Hospital in McKeesport, and their disparate schedules afford them little shared time.

“Well,” he says, “at least I got Monday and Tuesday off, so we try to put that Tuesday aside to have all day together. Otherwise, I’m just napping.”

Still, Fancher doesn’t necessarily mind his late hours. He enjoys the relaxed atmosphere of the graveyard shift, and says that the mood at night is preferable to the bustle he experienced when he used to work during the day. When he isn’t chatting with the other staff, making jokes, and trading gossip, Fancher likes to “people watch,” to observe the “stragglers” who occasionally spend the night waiting in the airport lobby.

“You learn by watching these people, learn their psychology,” he says. “There’s hot and there’s cold; sometimes people ain’t morning people, and sometimes they ain’t night people, but the stragglers all got the same patterns.”

Fancher says that when people are held at the airport overnight, waiting on delayed flights, they sometimes try to make conversation, sometimes read a book.

“Or usually do that,” says Fancher, chuckling and gesturing to a man slumped down in a black lounge chair, deep in slumber. “Now you know that’s where I want to be.”

The only other straggler here tonight is Sharon Lissimore, of nearby Niles, Ohio, and she is wide awake, waiting for her daughter’s plane to arrive from fort Meyers, Florida. The flight, originally scheduled to land just past midnight, was delayed due to rainy weather, and Lissimore, 58, has spent the last few hours in front of a closed café, silently working on a crossword puzzle.

Though she is eager to see her daughter, and therefore doesn’t mind the wait, Lissimore says that being in the airport so late at night is “more than a little eerie.”

“Nothing’s open at all,” she says. “I’ve never seen it so quiet. [It’s like it’s] full of ghosts.”

But after pausing a moment and pointing to a security guard leaning against his post, she adds: “I guess it’s busy, though, too. There are more people here at work than I would have thought.”

Fancher says that Lissimore’s reaction to the night workers is common.

“Most people don’t know how much gets done around this hour, how much work we do now even though it’s so empty,” he says. “Most everything gets done here before morning.”

Yaros, who has a second job, agrees.

“The late shift here is busier than the construction work I do during the day,” he says. “Jobs like that have a start and an end — like when you go to the store, but then at night it closes. The airport … is a place that never really sleeps.”

It will be a few hours before Fancher and Yaros get any sleep of their own. Then, as the day’s first travelers arrive for their 6 a.m. flights, the sun will rise over the airport parking lot and shine brightly on out-of-state license plates. But for now, the night crew is awake, working quietly, steadily, in an entirely different light.