This post comes from Darren Booth at partner site CNBC.

Time is running out to qualify for coveted elite frequent-flier status for 2013. And many travelers are making "mileage runs" this month to hit their mileage goals by year's end.

Airlines calculate elite status on the amount of miles flown in a given calendar year. So fliers short a few hundred (or even thousand) miles often resort to taking trips for the sole purpose of racking up the needed miles for silver-, gold- or platinum-level benefits.

I'm one of those fliers. I got my mileage run out of the way earlier in the year to avoid potential flight cancellations and delays, often related to December weather.

In September, I flew from Los Angeles to San Juan, Puerto Rico, and back in the same day just to accrue the roughly 7,000 miles I needed to requalify for United's top-tier Premier 1K status. It requires 100,000 miles of total flying in a calendar year, and the benefits I earn far outweigh the $320 I spent on the ticket (and my time for the day).

Had I not flown those additional miles, I would be Premier Platinum in 2013, which in itself is still pretty good. But achieving the top-tier 1K status gives me the following perks not available at the Premier Platinum level:

• 25% more bonus miles for each flight taken during 2013.
• Higher priority for complimentary upgrades, wait lists and standby clearance.
• Instant upgrades to first class on midpriced coach tickets when flying domestically.
• Access to a dedicated call center line staffed by U.S.-based agents.
• A $60 statement credit on my United MileagePlus Chase Visa credit card.
• Six Global Premier Upgrades for use on international flights.

Many hardcore frequent fliers also make a game out of mileage running by trying to find the lowest-priced ticket that earns the most miles. Members of the online frequent-flier community Flyertalk.com post their finds in a dedicated mileage run forum.

Another website, TheFlightDeal.com, publishes low-cost tickets that earn lots of miles. THe site also provides step-by-step instructions on how to search for availability and book tickets. A recent example reveals that you can earn 5,038 miles on United for $167 by flying round-trip from Philadelphia to San Diego.

Mileage runs and how to find them were also discussed in detail at Frequent Traveler University earlier this month in Los Angeles.

More from CNBC and MSN Money:

• AAA forecasts more Americans will travel this holiday and spend more
• Long layover? Many airport hotels offer day-room rates
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• Smart Spending on the go: Get our app for Android or iPhone
• American Airlines has a new kind of fee
• 12 ways to land lower airfare