Not long after the lifts stop spinning and the sun approaches the end of its westward trek, a ghost army of skiers equipped with alpine touring (AT) gear begins its march uphill. As darkness falls, from the highway you can see the halos of their headlamps, intermittent orbs of halogen glowing in the dark like strands of holiday lights snaking up Riva Ridge and Simba, the designated uphill routes on Vail Mountain (ditto Gold Dust, Sawbuck, and Little Brave at Beaver Creek, Bachelor Gulch, and Arrowhead).

At the summit, after locking heels of articulated boots and bindings into downhill mode and ripping sticky-backed climbing skins from skis, they point their tips downhill, falling into the abyss of cold and wind and emptiness that is night. Enveloped in black, carving turns on hardpack aglow with the diffuse light of stars and moon, it’s as close as a skier can come to flying while gliding on snow, experiencing a mountain that is a wholly different place than the one most skiers know only by day.

“It’s just you and the mountain, and it’s quiet,” says John Plack, Vail Mountain’s senior communications manager, who usually begins huffing up the skintrack from the Lionshead ski yard not long after clocking off work. “There’s minimal people out there, and those who are out there tend to be out there for the same reason: they’re getting their exercise in, they’re getting in that nice end-of-day mental headspace, whatever work they were dealing with during that day. Everyone’s friendly, everyone waves, and it’s just kind of nice.”

Want in on the fun, but don’t know where or how to begin? Look here for all the answers to your AT FAQs.

Where can I rent AT gear (specialized boots, skis, and poles)?

Alpine Quest (34510 U.S. Hwy 6, Edwards; 970-926-3867; alpinequestsports.com; $95/day) and Cripple Creek Backcountry (82 E Beaver Creek Blvd, Avon; 970-763-5723; cripplecreekbc.com; $120/day)

What should I wear?

A waterproof shell top and bottom (if it’s snowing) with a moisture-wicking base layer, hat/balaclava, and glove liners for dumping heat on the uphill; goggles and an extra thermal layer, including ski gloves, for staying warm on the downhill

Anything else I need to bring?

A day pack for carrying extra layers, at least a quart of water in an insulated container (to replenish moisture lost to sweat and exhalation), energy bars (because you’ll burn calories), a headlamp with extra batteries, and a fully charged cellphone (ideally with backup battery)

Where is AT skiing allowed on the mountain?

Only on designated uphill routes (Riva Ridge on Vail Mountain, Simba on Lionshead, Gold Dust on Beaver Creek, Leave the Beav/Sawbuck on Bachelor Gulch, Little Brave on Arrowhead); routes are subject to closure due to snowmaking or grooming operations.

How do I know which routes are open or closed?

Always call the Trails Hotline at each resort before you head out: 970-754-1023 (Vail), 970-754-5907 (Arrowhead, Bachelor Gulch, Beaver Creek).

Can I use uphill routes during normal operating hours?

No. Uphill access begins 30 minutes after lifts stop running and ends 15 minutes before first chair.

Do I need a ski pass?

No. Unlike Aspen Skiing Company (which this season requires users to purchase and carry a $69 uphill ski pass), Vail Resorts does not charge for uphill access.

Can I ski with my dog?

Dogs are prohibited on all resort terrain (AT skis have sharp edges and can seriously injure even your most well-behaved best friend).

Is ski patrol on duty if I happen to injure myself, get lost, or need help?

No. If you have an emergency after hours, call or text 911, and Vail Mountain Rescue Group, Eagle County’s all-volunteer search-and-rescue team, will respond, free of charge.

What if I want to AT ski in the backcountry?

In addition to the gear above, you’ll need to carry (and know how to use) an avalanche beacon, a probe, and a shovel; if you lack the experience (or skill), hire a professional: Paragon Guides (970-926-5299; paragonguides.com) offers private guided backcountry ski tours from $195/person.