If they don't have a frequent-flier ID card, travelers check in online or at kiosks and get a bar code on a printed boarding pass or on a mobile phone, just like at other airlines.

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Apply the same logic to customer loyalty programs like frequent flier miles, credit card rewards and online club accounts.

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Think of credit card companies offering frequent flier mile bonuses or discount brokers enticing IRA rollovers with cash bonuses.

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American, by contrast, said that 62% of the 185 billion frequent-flier miles it issued last year went to customers as credit-card rewards, not flying in airplanes.

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Mr. Lin said he's a frequent flier-mile "junkie" himself who will turn over at least one card a year.

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In a bit of good news for those who hunt for frequent flier miles, American Express is giving away 100, 000 miles Delta SkyMiles a week to card holders in the Midwest, the Detroit News reports.

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Frequent-flier miles themselves generate billions of dollars in revenue for airlines, which sell them to credit card companies and others which then offer miles to consumers as rewards.

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