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.

Airlines are increasingly rewarding wealthy fliers with something more intangible: physical distance between them and everyone else.

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.

So some airlines scrapped the ultra-premium cabin.

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.

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