Herb Kelleher, who co-founded pioneering low-cost carrier Southwest Airlines and built it into an industry powerhouse stamped with his colourful, unconventional personality, died on Thursday at the age of 87, the US carrier said.

Ryanair paid tribute to Mr Kelleher who advised chief executive Michael O’Leary to turn the airline into a low-cost carrier in the late 1980s.

“RIP and thank you, Herb Kelleher ,” the airline said in a tweet early on Friday.

“Herb was the Grand Master Yoda of the low-fare airlines. He was the leader, the visionary and the teacher: without Herb there would be no Ryanair, and no low fares airlines anywhere,” added Mr O’Leary.

Mr Kelleher set up Southwest with Rollin King more than 50 years ago, with the airline making its first flight in June 1971. Mr King died in 2014, aged 83.

Dallas-based Southwest is known for its quirky culture, closely connected with Mr Kelleher’s maverick image, as well as its fast growth from a regional carrier into one of the biggest in the United States.

The airline flew short flights known as point-to-point, rather than the hub-and-spoke model of its bigger rivals, and used a single model of aircraft, Boeing 737s, to cut complexity and cost.

Forerunner

Southwest “rewrote airliner service in the US [and] became the forerunner of many, many low cost carriers across the globe,” aviation analyst Scott Hamilton said in aerospace publication Leeham News.

Southwest’s cabin crews have become known for their good humour – a legacy of Mr Kelleher, memorialised in a “laugh button” that visitors could press inside the company’s headquarters to hear his famous cackle.

Mr Kelleher won the affection of customers and employees with low fares, good wages and his own high spirits. He sought to instil a sense of fun among employees, sometimes showing up in costume or helping unload baggage.

“A company is stronger if it is bound by love rather than by fear,” he was once quoted as saying.

Mr Kelleher was known for his fondness for smoking and bourbon but he was a formidable industry competitor as well.

“There aren’t a whole lot of individuals who you can point to that single-handedly contributed to building a demonstrable portion of the modern economy. Herb Kelleher was one,” tweeted Jon Ostrower, an independent aviation commentator and editor of TheAirCurrent.com.

“His model spawned the global democratisation of the affordable movement of humanity by air.”

The New Jersey-born Kelleher served as Southwest’s executive chairman for 30 years until 2008 and was chief executive from September 1981 to June 2001.

Mr Kelleher was long a towering figure in the US airline industry along with Bob Crandall, his rival at American Airlines and polar opposite in style. The two built different business models and competed fiercely but with mutual respect.

Steven Udvar-Hazy, executive chairman of Air Lease and a pioneer of the aircraft leasing industry, whose expansion coincided with the rise of budget carriers, paid tribute to Mr Kelleher as “the builder of the world’s most successful low-fare airline.”

“Herb: a final Wild Turkey bourbon toast from all of your closest friends,” he added. – Additional reporting: Reuters