If you've ever seen the movie "Up in the Air," you probably turned a shade of green as the film's protagonist, Ryan Bingham (George Clooney), estimated that his mileage balance neared 10 million. Bingham earned his miles the old-fashioned way — flying around the country firing people while his company picked up the tab. Lucky for you, you don't have to travel millions of miles to earn a free trip. Here are five ways you can collect miles without ever stepping foot on a plane.

See: Delta and United Put a Price on Loyalty – Should You Pay It?

Credit cards are the easiest way to give your mileage account a boost. With sign-up bonuses ranging from 25,000 to 100,000 miles, you can feasibly cover at least one round-trip economy flight to anywhere in the U.S. Or, splurge all 100,000 miles on a business-class trip to Europe. Either way, you can get $300 or more in value out of a single credit card sign-up bonus.

The only catch to these sign-up bonuses is that cardholders will need to meet certain spending requirements, which are typically around $3,000 within three months of opening the account. Meet these requirements by charging all household spending — including mortgage and rent payments — to the card. 

If you're averse to the idea of acquiring new credit cards to off-set travel expenses, there are a few alternatives. Though mile-earning debit cards offer paltry sign-up bonuses that aren't even worth mentioning, they do earn between 0.5 miles per dollar on all spending. The UFB Direct Airlines Rewards debit card earns 0.5 American Airlines AAdvantage miles per dollar. Meanwhile, residents of Hawaii can earn 0.5 HawaiianMiles per dollar with the Bankoh Hawaiian Airlines Visa Check Card. The earning potential isn't as high for debit cards, but it's a worthy alternative for those who don't have the credit score (at least 700) to obtain credit cards or they simply don't like dealing with them.

Those with large amounts of cash lying around can earn a more impressive payday with Fidelity. The brokerage firm offers upwards of 50,000 AAdvantage miles for cash deposits into a qualifying brokerage account. There's no need to use the funds — simply transfer the balance into your brokerage account, leave it there for nine months, and your points will automatically be credited to your account. As an added bonus, the balance will earn interest.

BankDirect, an online-based bank, allows account holders to earn upwards of 21,000 AAdvantage miles for a variety of banking activities as well as a bonus of 100 miles per month for every $1,000 in the account. It's earning miles without having to think about it. What could be easier than that?

See: How to Get Upgraded on Your Next Flight

Nearly every major airline, hotel and bank rewards program has a shopping portal that enables members to earn at least one extra mile per dollar for shopping online. Many portals offer first-time bonuses and periodic incentives for buying specific items or shopping with certain merchants. Sometimes these bonuses are so lucrative that travel hackers will buy merchandise and resell it for the airline miles alone.

Sign up for an account with the major shopping portals and opt in to receive email notifications in case of lucrative promotions. Online shopping portals can offer bonuses far more profitable than any credit card category bonus. To search for the highest payout at your favorite online merchant, check with CashbackMonitor.com or CashbackHolic.com before you shop.

As with shopping portals, most major rewards programs offer dining rewards programs of their own. These programs allow members to earn points when they dine at more than 10,000 participating restaurants. All you need to do is sign up with the dining rewards program of your choice, register your credit card and the next time you dine at a participating restaurant, you'll automatically earn up to eight points per dollar on your bill.

In addition to paying out upwards of eight points per dollar, every dining rewards program offers a bonus of 500 to 2,000 points for new members who dine at participating restaurants within 30 days of signing up.

While you can register with as many rewards programs as you want, don't join more than one unless you plan on dining enough to earn the new member bonus for each one. It's also worth noting that the same credit card can't be registered with more than one dining rewards program at a time.

See: The Best Airline Rewards Programs of 2014-15

This isn't the most lucrative way to generate miles, but if you have a few minutes to spare each day, sites like e-Rewards.com and e-Miles.com make it possible to earn miles for completing surveys. You certainly won't generate enough for a trip to Europe, but it is a free way to earn a few hundred miles each month. As an added incentive, sometimes e-Miles will offer bonuses for charitable donations to reputable organizations.

Whichever method you choose, just remember that by ensuring that every dollar you spend earns the most miles possible, you can travel virtually anywhere at a fraction of the cost.  

Ariana Arghandewal is a travel writer who enjoys helping others navigate the world of travel hacking though her blog, Pointchaser. You can follow Ariana on Twitter or connect with her on Google+.

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