Some U.S. airlines have special mileage-point bonus programs for only their most elite frequent flyers -- the travelers who reach 1 million mileage points or more.

Achieving elite status in airline frequent-flyer programs takes a lot of travel: an annual minimum of five coast-to-coast round-trips (or equivalent) for the bottom rung of the elite status ladder, up to 50,000 miles for middle-tier membership and 75,000 to 100,000 miles for hardest-to-hit top tier.

To maintain this hard-earned status means flying the same number of miles year after year.

When frequent travelers finally retire they usually don't mind traveling less frequently but when they do make a trip they crave their customary perks.

For them good news! Some airlines now give special treatment to members who accumulate 1 million miles or more. These unpublished programs reward over 250,000 top travelers at American Airlines, Delta Air Lines and United Airlines with complimentary lifetime privileges.

These privileges include free upgrades to first or business class, bonus miles, priority seat selection and boarding, separate security lines and special reservation phone numbers.

As with the standard frequent flyer programs, benefits and qualification vary from airline to airline, particularly when it comes to complimentary upgrades.

American makes it easiest to become a million miler because miles from any activity -- including partner credit card spending -- count towards the threshold.

Delta offers the ultimate prize of lifetime top-tier status at 4 million "flown" miles, but the best reward is probably with United, where a million "flown" miles earns Premier Executive status: this mid-tier membership usually requires 10 transcontinental roundtrips every year.

The table that accompanies this article (see click-to-enlarge version of the image) details the status levels and benefits that American, Delta and United award travelers who accumulate 1 million mileage points or more and how the points must be earned.

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