NEW YORK: On flights from San Francisco to Hong Kong, first-class passengers can enjoy a Mesclun salad with king crab or a grilled prime beef tenderloin, stretch out in a 3-foot-wide seat that converts to a bed and wash it all down with a Krug “Grande Cuvee” Brut Champagne.

Yet some of the most cherished new first-class perks have nothing to do with meals, drinks or seats. Airlines are increasingly rewarding wealthy fliers with something more intangible: physical distance between them and everyone else.

The idea is to provide an exclusive experience – inaccessible, even invisible, to the masses in coach. It’s one way that a gap between the world’s wealthiest 1 percent and everyone else has widened.

Many top-paying international passengers, having put down roughly $15,000 for a ticket, now check in at secluded facilities and are driven in luxury cars directly to planes.

When Emirates Airline opened a new concourse at its home airport in Dubai last year, it made sure to keep coach passengers separate from those in business and first class. The top floor of the building is a lounge for premium passengers with direct boarding to the upstairs of Emirates’ fleet of double-decker Airbus A380s. Those in coach wait one story below and board to the plane’s lower level.

London’s Heathrow Airport took a private suite area designed for the royal family and heads of state and in July opened it to any passenger flying business or first class who’s willing to pay an extra $2,500.

“First class has become a way for a traveler to have an almost private jet-like experience,” says Henry Harteveldt, an airline analyst with Hudson Crossing. Airlines “will do everything but sing a lullaby.”

The front of the plane has always been plusher. But in recent years airlines have put a greater focus on catering to the most affluent fliers’ desire for new levels of privacy.

There’s a lot of money on the line.

At carriers like American Airlines, 70 percent of revenue comes from the top 20 percent of its customers.

The special treatment now starts at check-in. American and United Airlines have developed private rooms, located in discreet corners of their terminals in New York, Chicago and elsewhere, that allow for a speedy check-in. Boarding passes in hand, travelers exit through hidden doors leading to the front of security lines.

Some foreign airlines have gone further. Lufthansa offers first-class passengers a separate terminal in Frankfurt. There’s a restaurant, cigar lounge and dedicated immigration officers. For those who choose to shower or take a bath, the private restrooms come with their own rubber ducky – an exclusive plastic souvenir for the international jet set. When it’s time to board, passengers are driven across the tarmac to their plane in a Mercedes-Benz S-Class or Porsche Cayenne.

“That sort of exclusivity plays to the ego of people who are in a position to spend that much money on an airline flight,” says Tim Winship, publisher of travel advice site FrequentFlier.com.

At Heathrow’s private suites, designed for up to six people, fliers pass swiftly and privately through their own immigration and security screening. While they’re waiting, hors d’oeuvres and Champagne are provided. Steak, sushi or other meals can be delivered from airport restaurants. When it comes time to actually fly, passengers are driven to their plane in a BMW 7 Series sedan and escorted to their seat.

Want to board first? No problem. Want to be the last one seated, moments before the door closes? Sure. Airlines will even save room for your bags in the overhead bin.

International first class has long been distinguished by gourmet meals, wide seats and giant TVs preloaded with hundreds of movies and TV shows. But in recent years, airlines also upgraded their international business class sections, ripping apart cabins to install chairs that convert into lay-flat beds. That left very little to differentiate first class from business class.

So some airlines scrapped the ultra-premium cabin. Others have cut the number of first-class seats in half, creating a more intimate experience that commands the higher price. For instance, a roundtrip flight in July between New York and Hong Kong on Cathay Pacific costs $1,600 in coach, $7,600 in business class and $19,000 in first class. Other airlines charge similar price differences among their passenger classes.