Whether you're just starting or have earned airline miles for decades, travelers need to ask themselves: "Is it better to earn miles across several airlines or concentrate earnings on just one airline?” Let's discuss the pros and cons of joining multiple airline rewards programs.

The pros

Earn miles on every flight

The most straightforward reason to join multiple airlines rewards programs is to be rewarded for every flight you take. After all, even if you earn just a couple of hundred miles from a flight, those miles can add up over time.

Many U.S.-based airlines — including Delta, Southwest and United — have eliminated mileage expiration. On these airlines, you can accumulate miles toward a reward flight as slowly or quickly as possible without worrying about losing miles due to inactivity.

Also, over the past few years, airlines have added redemption options that require fewer miles. For example, you no longer need to accumulate 12,500 miles to book a one-way award flight. Instead, you can now book award flights with just a few thousand miles through dynamically priced awards.

Score bonus miles for joining as a new member

Although U.S.-based airlines rarely offer new member bonuses, many international airlines will offer new members bonus miles. Sometimes these are paid as a bonus just for signing up. For instance, TAP Portugal offers all new members 200 bonus Miles&Go miles just for joining.

Other new member bonuses require that members complete flights before earning a bonus: New Etihad Guest members earn 500 bonus miles after their first flight.

Just be sure to have a utilization plan for that airline rewards program before signing up. Earning bonus miles in these programs doesn't get you anything if the rewards expire.

Earn miles from non-flying activities

Another reason to join multiple reward programs is to open more ways to earn miles.

In addition to earning miles from flying, airline loyalty programs let members earn miles through online shopping portals, hotels and car rental partners, dining programs, and other activities. These partnerships and promotions vary between programs, so being a member of multiple programs can pay off.

For example, Delta is unique among the major U.S. airlines in partnering with Instacart, Lyft and Airbnb. If you want to earn airline miles through these partners, you'll need to be a SkyMiles member.

Meanwhile, American Airlines and Hyatt have partnered to give World of Hyatt members 1 World of Hyatt point per $1 spent on American flights. But, you'll need to be an AAdvantage member and link your accounts to gain more rewards on your flights.

Another example: Southwest Airlines recently offered a mystery bonus to earn up to 1,000 bonus miles for spending $300 through its Rapid Rewards shopping portal.

No other airline shopping portal offered a similar bonus that week. That meant the only way to earn bonus miles from online shopping that week was to be a Rapid Rewards member and shop through the Southwest Rapid Rewards shopping portal.

Unlock perks for linking accounts

Scoring more perks by connecting accounts is another reason to join additional airline rewards programs.

Marriott Bonvoy Titanium Elite or Ambassador Elite members can claim United Silver elite status by linking their Marriott and United accounts. That's enough to get perks like free extra-legroom seating at check-in, upgrades to first class, free checked bags and bonus miles.

If you don't care about earning United miles, linking your accounts and claiming reciprocal elite status also unlocks the ability to transfer any United miles you have to Bonvoy points.

The downsides

No (immediate) incentive to do so

Unless you plan to earn miles in the program or earn a new member bonus, there are no other incentives for joining multiple airline rewards programs.

Unlike hotel loyalty programs, airlines don't provide members perks like free Wi-Fi or waived fees just for being a member. So, the only reason to join multiple airline rewards programs is if you're going to start earning miles through that program.

It takes time to enroll and manage accounts

Joining airline rewards programs takes time — from going through the enrollment process to dealing with all of the account statements and promotional emails that you'll start getting once you're enrolled.

Focusing your earnings may lead to more perks

Sure, you can earn a couple of hundred miles in several programs. However, if you want to build up a usable balance sooner, you should focus your earnings on one or two programs. In addition to using reward miles sooner, concentrating your earnings may also yield more perks faster.

Even entry-tier elite status can provide some nice benefits. For example, American Airlines AAdvantage Gold status members earn perks such as:

Upgrade eligibility on all domestic American Airlines flights.

Netting 40% bonus miles on flights.

A free checked bag.

Obtaining extra-legroom seats at check-in for free.

Delta and United offer similar perks for their entry-tier Silver elites.

Scoring perks like these can justify focusing your mileage earnings on one program, even if you might get a few more miles or a slightly cheaper flight on another airline.

Increased risk of data leaks

Another downside to joining multiple airline rewards programs is the potential of having your personal data leaked. When you join an airline loyalty program, you need to provide personal information generally including:

Your name.

Date of birth.

Address.

Email address.

Phone numbers.

Unfortunately, we've seen data leaks occur at overseas airlines from Air India to British Airways. While data breaches seem ubiquitous nowadays, signing up for another airline rewards program can increase the chances of your data being leaked.

Should you join multiple airline rewards programs?

Joining multiple airline rewards programs can open the door to earning miles on every flight, some non-flight activities and partnerships, from hotel stays to shopping on Instacart. Airlines sometimes even offer a new member bonus to incentivize you to join their program.

However, joining several airline programs has its downsides. It takes time to enroll and manage accounts and having your personal information in more places increases the potential for your data to be leaked. Plus, there's no incentive to enroll in yet another program unless you plan to utilize it.