You may think airports are primarily about one thing: shopping.
That's right. Not flying -- that's what you do after you've had your credit card stretched on gallon bottles of duty free eau de parfum and single malt.
But there's yet another activity -- or, rather, inactivity -- apparently important for rating airports: sleeping.
Started 17 years ago as a guide for budget travelers on where to snooze in airports worldwide, to save on accommodation during a long layover, Sleepinginairports.net claims now to have wider relevance.
"Airport sleeping is no longer just for the cheap young backpacker," the site says.
"Nowadays, early morning flights ... flight cancellations, snowstorms and erupting volcanoes are just a few reasons why you'll see people of all ages and incomes stretched out on airport floors around the world."
Airport sleeping essentials
Sleepinginairports asked 14,600 passengers to rate airports according to four sleep-related criteria -- "the four C's."
"Comfort" includes armrest-free seating -- all the better for stretching out on -- and quiet zones.
"Convenience" encompasses 24-hour food and showers.
"Cleanliness" is more general, including clean bathrooms and food courts.
"Customer service" covers those unexpected extras that make you remember a place with affection, such as "airport workers who ... give us blankets and pillows when we're stranded."
So, how did the airports do?
Try to stay awake now!
Best airports for sleeping
5. Helsinki-Vantaa Airport
Some might say Helsinki itself is pretty soporific so this snooze-friendly airport should really knock you out.
"There are benches all over the place," writes one Sleepinginairports voter, the amusingly named Sleeping Around.
Never mind that that commendation sounds like something you might overhear at a tramps conference, Vantaa has a book swap, airport tours and a Relaxation Zone with a whole smorgasbord of seating types to keep the restless, or rest-seeking, passenger satisfied.
"If you can't find a way to sleep in this airport, there might be something wrong with you," concludes SleepinginAirports.
4. Hong Kong International Airport
"There are a few 'beds' made of four seats together (no armrests)," coos airport sleeper thisisme.
"Look for the lounge chairs hidden behind shrubbery," the site adds.
3. Amsterdam Schiphol
A new entry to the site's top three, Schiphol scores for its "comfortable couches," a museum and a forest-like area between Departures 3 and 4 complete with nature sounds.