A bridesmaid is able to enjoy all of her friends' wedding thanks to Southwest Airline's low fares.

To help us identify that Southwest “secret sauce” we mentioned earlier, we talked to a lot of people. The agencies and Southwest did lots of qualitative, exploratory research with consumers, validated by quantitative research. We wanted to discover what made the brand’s loyalists so loyal and what makes Southwest Airlines completely and utterly unique. We also talked to employees and management to better understand where the brand was coming from and where it was headed.

After hundreds of peanut M&Ms and mentions of the word stimuli, we found that Southwest’s difference sits at the intersection of some of the most powerful forces a brand can corral: culture, the consumer and the category itself. There was a strong desire for a different kind of airline—one that puts people first; one with the integrity, empathy and courage to challenge the status quo. Though these qualities had always been a part of the brand’s core, it was time to bring them front and center and to claim a space that no other airline could—Southwest is the only airline with heart.

For the first time in its 43-year history, Southwest has a single logo and a unified brand look and feel. The rebrand is seen and felt at every touchpoint—from the planes themselves to a custom typeface featured in all channels to the airport experience, website, billboards, TV commercials and more.

The response to the rebrand has been phenomenal. Longtime fans love it; new customers are drawn to it. The entire organization from top to bottom has wholeheartedly embraced it and has been energized by it. The heart icon is now serving as a guiding symbol for all brand communications.

Accolades include:

2015 ATW airline of the year

21% return on invested capital

Stock price up 125% since rebrand

Number one performing stock of the S&P 500 for 2014

#7 on FORTUNE World’s most Admired Companies list for 2015 (the only airline in the top 10)

FORTUNE’s Most Admired list