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We've all heard the rumors. If you dress up and tell a compelling story—maybe you're leaving for your honeymoon or heading to a funeral—you might finagle a free first class upgrade. But there's a problem: upgrades rarely happen. Years ago, it might have been possible, back when airlines struggled to sell those cushy seats up front. With an improved economy, however, many travelers have been buying first and business class seats, leaving fewer for upgrades. Even if airline employees wanted to make your day, they don't have much inventory to work with.

"There is no way to sweet talk or dress yourself up into an upgrade," says Jaime Fraser, a Virgin Atlantic spokeswoman. "If our airport staff are looking to upgrade passengers on the day of departure, there is a process that they follow which generally sees passengers that are frequent fliers of the airline—or those that have paid for a fully flexible ticket—benefiting."

On Virgin Atlantic, as at most airlines, upgrades into unsold seats tend to go to an airline's most loyal passengers, people who spend thousands of dollars each year on the most expensive tickets. A few years ago, these elite fliers could often count on freebies, especially when traveling within the United States. But now, even many of them must wait until the last-minute before they get the call to first class—if they receive it at all.

That's not to say that trying to game the system is completely hopeless. Millions of Americans fly every month, and while it is becoming increasingly rare, plenty of passengers fly in first class without paying for it.

Here are some strategies for scoring a free upgrade.

1. Fly a lot.

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(Etihad Airways)

This is the most common way to earn a free upgrade. Most airlines reserve some space for travelers who fly at least 25,000 miles per year, with the best perks going to 100,000-plus-mile fliers. As recently as five years ago, this meant half or more of domestic first class fliers sat up front for free. But now, airlines are selling more premium seats, so on popular routes, such as Los Angeles to Chicago, it is not unusual for more than 40 elite fliers to compete for one or two upgrades. Airlines usually prioritize who gets them based how many miles a passenger flies per year and what they paid for their coach ticket. On routes with fewer business fliers—think New York to West Palm Beach—free upgrades remain more plentiful.

2. Use miles.

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ZAGREB, CROATIA - MARCH 2, 2015: Photo of Air France - KLM card and other cards in wallet. Flying Blue, the frequent flyer program of Air France - KLM, awards members points based on miles travelled and class of service. (iStock)

If you're not an elite frequent flier but still have some miles banked, you may be able to use them for an upgrade. Be careful, though, as many airlines now ask not just for miles but also a cash co-pay. One example: On flights to Europe, American Airlines charges 25,000 miles, plus $350, for a one-way upgrade from discounted economy to business class. For most domestic upgrades, American wants 15,000 miles plus $75.

3. Get lucky.

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african businessman at airport waiting for flight (iStock)

Sometimes airlines overbook coach, and a few passengers get bumped up, only because no seats remain in back. Agents try to ensure the airline's most loyal passengers get the nod, but sometimes things get frenetic and employees make more random decisions. "Agents usually have some flexibility to make sure the plane gets out full and on time," says Gary Leff, who runs frequent flier blog View From the Wing. "So if it's the easiest way for them to do it, they might upgrade someone else out of order."

4. Save a life.

Group of paramedics with patient

Group of paramedics carrying patient on a helicopter ambulance (iStock)

Flight attendants don't usually upgrade passengers, even when empty seats remain. Unfortunately, sob stories don't work as currency. One exception: medical personnel. Doctors and nurses who answer an emergency call are sometimes an exception. If they stabilize a passenger, flight attendants might allow them to sit in business or first class for the rest of the flight.

Check out more of the best ways to get upgraded on your next flight. 

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