Here's how you can get air miles without actually flying

Collecting air miles can make flying a lot cheaper, and help you get a free upgrade.

But many people who aren't frequent fliers are put off by air miles because they think they have to spend a substantial amount of money on flying with the same airline before they can reap the benefits.

What most people don't know, however, is that there is a simple way to rack up air miles without even flying: by shopping online through airline websites, according to the frequent flier and air miles expert Gilbert Ott, who runs the flight deal site God Save the Points.

A number of airlines like British Airways and Virgin Atlantic offer members of their point schemes access to shopping portals via their websites that link to popular retailers. By making a purchase on those retailers' websites - when accessed through an airline's shopping portal - the user is rewarded by the airline with a certain number of points or miles for every pound or dollar they spend.

Ott considers this "the most overlooked" way of getting air miles. It often works out to be more lucrative, too.

"For most people who are economy fliers, [flying] is the worst way to earn miles," he said, adding that with most airlines "you get less than a mile for every mile you fly."

Whereas, through airlines' shopping portals, users can often collect more points per pound or dollar they spend. For example, British Airways' Gate 365 portal allows members of its Executive Club - which is free to join - to earn up to 30 Avios points (the airlines' version of air miles) for each pound they spend on online purchases. Each store available through Gate 365 - which include John Lewis, Net-a-Porter, and Selfridges - offers a different number of Avios points per pound spent.

Here's what the page looks like. Unfortunately this is what it looks like fully loaded (the website could use some work):

After speaking to Ott, I bought some items I needed on John Lewis' website through Gate 365. My total came to £48 ($62), which will earn me 192 Avios points, four points per pound spent. Admittedly, I'll need a lot more than 192 points to get a free flight - you can only begin to save money on flights once you've reached 5,000 Avios points, according to the Avios calculator - but it's a start.

To get the most points, Ott suggests shopping through airline portals as much as possible, but especially when you need to make particularly expensive purchases like a laptop, which he said might buy you an entire round-trip ticket, or around the Christmas season, when you're spending a lot of money on gifts. "Eventually, those transactions add up," he said.

Another benefit of using this method is that you don't need a special credit card - or one that promises air miles - to get miles with a purchase.

"You don't actually have to have an airline credit card to earn miles from home for many of the daily things you do," Ott said. "People really miss out on [this option] entirely."

This way of collecting air miles is one of the reasons why Ott thinks "frequent flier miles is a really bad term." He believes that "you don't have to be a frequent flier or even a flier at all to earn the rewards that will get you free travel."

Though earning miles through online shopping won't automatically give you enough points for free travel, Ott sees it as a way to turn an everyday activity into cheaper travel in the long term. This is why he loves air miles, he says - because they can make travel "affordable to everyone."