First class looks inviting in Aeromexico's Boeing 787-9 Dreamliner plane, in Mexico City. (Pedro Pardo/AFP/Getty Images)

Traveling on an airplane is an increasingly frustrating experience. Whether it is the tight space, the irritating seat recline, the absence of free food or the flight attendant's inattention, air travel is becoming more of a hassle every year. At least in economy class.

No wonder the marvels of first-class travel have become a viral YouTube success. In a clip that has reached 24 million views so far, New York-based blogger Casey Neistat is seen eating caviar in his private Emirates Airline cabin, lying down on a full bed and even taking a shower. He seems so happy and amazed, and you instantly feel it was a dream come true.

Neistat claims that he received a free upgrade from business class. Normally the ticket would have cost him $21,000 — at least that's the amount he mentions in the video. A quick search on Emirates’ website reveals, however, that you can get the same flight for half that price.

But the question remains: Does anyone really spend that much money for a flight from Dubai to New York? And if yes, who are these people?

According to airlines and travel experts, those first-class comforts are enjoyed mostly by wealthy individuals and a few corporate executives who usually pay the full price. In one post on the Quora question-and-answer website, Stephanie Vardavas, a frequent flyer from Portland, Oregon, tells about her experience with a first-class flight to the Australian Open in Melbourne. She noticed that the cabin was “populated solely by TV people,” such as NBC or ESPN commentators. Vardavas said she uses frequent-flyer miles to upgrade to first class when traveling internationally — a common choice among passengers choosing premium seats.

“First class on long-haul routes is generally a good mixture of upgraders and self-payers,” said Seth Kaplan, managing partner at Airline Weekly. “There are only a few companies left that allow employees to travel first class today.”

The Washington Post asked airlines about the characteristics of their first-class customers. While most didn’t provide an answer, Germany’s Lufthansa said that its guests in premium seats “mainly pay themselves.” According to a spokeswoman, only a “small part” of guests use miles to book or upgrade to elite services.

At some airlines, travel experts said, first-class seats have evolved into a way to reward loyal customers who have reached an elite status in frequent-flier programs or are using special services such as an airline's private jets.

“The percentage of real first-class passengers that specifically booked the ticket and paid the standard price is slowly declining to a low, one-digit figure,” said Matthias Levinger, chief executive of Vornesitzen, a German travel agency that specializes in high-class travel. Levinger said that he regularly meets with airline representatives who tell him how hard it has become to fill premium seats for high prices.

According to a recent report from the International Air Transport Association (IATA), the growth of the airline premium segment as a whole (including business class) “has continued to lag behind that of economy.”

So, substantial discounts are more common. According to travel agencies, you can find transatlantic first-class fares as low as $ 4,000 — if you’re not picky regarding airline, stopover or time of day.

Levinger noticed that Middle Eastern airlines like Emirates and Etihad (whose elite cabins are like small apartments) are offering comparatively low prices on connection routes.

“It’s hard to imagine that they’re actually making money with this,” Kaplan said. Competitors have criticized Emirates and Etihad’s prices as unfair, alleging that the airlines are receiving government subsidies. Both airlines deny those claims.

But even if prices for first-class seats are more competitive than it seems, they’re still well above the rates of their counterparts only a few rows back. And that may be the biggest problem.

Many airlines have improved their business class to a comfort level that was once a unique selling point of first-class cabins. Even United Airlines offers flat-bed seats in business class, for example. In Emirates' business class, flight attendants pour you a glass of champagne at the bar. The relatively lower difference between the seat classes makes it harder to persuade passengers to pay extra for small amenities they can only enjoy for maybe up to 10 hours or so.

That’s why airlines are slowly withdrawing from their elite segment. In other words, first class is dying. Lufthansa, once a luxury enthusiast, has pulled first-class seats out of much of its long-haul aircraft. United is phasing out its “GlobalFirst” product. Airlines like Cathay Pacific or Singapore are not ordering first-class cabins for new jets.

Passengers might be dreaming of caviar and privacy, but ultimately not enough of them want to pay for it.