From modest beginnings - just a separate cabin with identical seating - business class has become almost the height of indulgence - although the dwindling number of airlines that still offer first class are competing to provide ever greater luxury. But, say critics, the very front of the aircraft rarely pays its way; more often first class is filled with people upgraded from the business section, or the airline's own staff.
The man who made the biggest upgrade in the business cabin was Richard Branson, who unveiled Upper Class when Virgin Atlantic began flying from London to New York 15 years ago. He felt he could deliver a first-rate product at business-class fares, and many rivals agreed. Numerous carriers have removed first class in favour of a "premium business" product - the newest is Business Elite on Delta. The Atlanta-based airline claims "the most personal space among all major carriers in business class".
Of the companies which still offer first class, British Airways is so proud of its sleeper seats that it has been fighting Singapore Airlines in the courts, claiming the Far East carrier copied its design. Swissair, which admits its first-class product has slipped behind the competition, is spending millions on an inflight revamp. And Malaysia Airlines now offers helicopter transfers to some of its first class passengers on Kuala Lumpur-London flights.
Because each carrier has been trying to develop a distinctive premium service, there is little consistency between airlines which have combined into alliances. Next year, someone flying Singapore Airlines from Asia to Los Angeles, then connecting to Mexicana, will notice plenty of differences in the business class product of the Star Alliance's newest members.
A final word to Richard Branson, who remains confident that Virgin Atlantic is still distinctive: "In our business class, with the stand-up bars, manicurists, masseuses and sleeper seats, we're still ahead of the game."