In October, Daniel Palen took a trip to South Korea -- but never actually went there. He hopped on an American Airlines flight from his home in Kansas City, Missouri, to Chicago, where he transferred to a flight to Dallas. From Dallas, he flew nonstop to Seoul, got off the plane, beelined to an airport lounge for a quick shower and an email check -- and then turned around and got right back on a plane to Dallas. The 23-year-old traveler never crossed the passport check into the country.  

Palen’s trip is known as a “mileage run” -- embodying the practice of booking a relatively cheap ticket to somewhere, anywhere, for the sole purpose of earning frequent-flier miles and achieving, or maintaining, elite airline status. For his six-leg trip, Palen earned 19,000 miles on American’s AAdvantage program and inched a little closer to Executive Platinum status, AAdvantage’s top tier, which requires accruing 100,000 miles in one calendar year.

“Some people think it’s crazy, but when you look at all the benefits you get -- free tickets, upgrades with elite status -- it’s worth it,” said Palen, an information-technology consultant who travels frequently for work.

But soon, Palen and his ultrafrequent-flying brethren may no longer be able to reap the rewards of such trips. The mileage run scheme took a big hit this year when both Delta Air Lines and United Airlines changed their frequent-flier policies, requiring a minimum amount of money spent in addition to miles earned to achieve elite status, as noted by Delta and the Wall Street Journal, respectively. Further blows are coming in 2015, when both airlines will begin awarding frequent-flier miles not on the basis of how many miles you travel, but on how much you pay for a ticket. Among the so-called legacy carriers left standing, only American Airlines has kept its program untouched -- for now. (Industry watchers say the airline is keeping changes to a minimum as it merges with US Airways, as pointed out by USA Today.)

There aren’t a lot of hacks or ways to cheat anymore,” said JL Johnson, a correspondent at AirlineReporter.com, who’s done several mileage runs of his own on Southwest Airlines. “Each year the criteria for obtaining the various elite levels continue to get more strict.”

And rising ticket prices make justifying a mileage run even tougher. “With the new revenue requirements in place, mileage running will rarely make economic sense, except in cases where a traveler is just a few miles and dollars short of an elite threshold,” Tim Winship, publisher of FrequentFlier.com, told BoardingArea.

The change in United’s program is one of the reasons Palen actually started to fly American Airlines. He had been a Premier1K member, the highest status available on United, for a couple of years. Using his United miles, he took a once-in-a-lifetime trip to New Zealand in April on United’s Star Alliance partner airlines, as reported on the Upgrd site. But United also recently changed its redemption policies, and Palen said it now will cost a lot more to book a Star Alliance trip. That -- along with United’s current reputation as a low-performing airline, as described by Fortune -- convinced him to shift his loyalties to American.

Still, discussions about how to carry out mileage-run strategies -- even on Delta and United -- are alive and well at websites such as FlyerTalk.com, where the Mileage Run Deals forum is hopping with activity. Brian Kelly, who blogs about maximizing travel reward points at ThePointsGuy.com, said that even with a revenue-based model, mileage runs could still be useful when airlines do, occasionally, offer some kind of blockbuster deal.

“When airlines offer bonus mileage promotions, such as Delta’s Double Medallion Qualifying Miles to and from Seattle, booking a cheap flight could earn you a disproportionate number of miles,” Kelly said. “Sometimes you can do a partial mileage run, where you get a cheap flight but actually want to go to the destination as well. This is what I did with my dad when we went to Istanbul on Delta for $576 roundtrip from New York. I was able to turn this mileage run into a great father/son trip.”

Kelly suggested following the FlyerTalk forums and sites such as Airfarewatchdog.com for discount tickets that are worth using for mileage runs. Flexibility is important: You want to snag a cheap deal when you see one. Airfare search tools such as the Hopper Flight Explorer and ITA Matrix Search let you search by dates to see what cheapest flights are available during a given time period.

For Palen, these tools are an important part of his mileage-run arsenal. And while he hasn’t yet reached the holy grail of mileage runners, top-tier elite status, he’s not worried. In addition to flying home to Denver for Christmas, he’s planned a last-minute jaunt to Dublin, Ireland, to earn the final miles that will push him into elite territory.

“That will be the last hurdle,” Palen said. “I think I’ll just cross 100,000.”