Airline chief Herb Kelleher, credited for his part in pioneering budget flights, has died aged 87.
The low-cost carrier Southwest Airlines Co, which he co-founded, stated that he died on Thursday.
He was well-known for developing his business into an industry staple by streamlining its services to drop the prices of travel.
Ryanair CEO Michael O'Leary said: "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."
Dallas-based Southwest, which was established in 1967 and began flying in 1971, is known for its unique culture and its fast growth from a regional carrier into one of the biggest in the United States.
It flew short flights known as point-to-point, rather than the hub-and-spoke model utilised by rivals, and used a single model of aircraft, Boeing Co's 737.
These moves formed the ethos behind its motto: “Low fares. Nothing to hide. That's Transfarency.”
"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 democratization of the affordable movement of humanity by air."
Mr Kelleher won the affection of customers and employees with low fares, good wages and his own high spirits – known for his standout laugh and sense of humour.
He sought to instil a sense of fun among employees and sometimes arrived at airports in costume or helped to unload baggage.
"A company is stronger if it is bound by love rather than by fear,” he was once quoted as saying.
He was also known for his fondness for smoking and bourbon.
John Plueger, chief executive of Air Lease Corp, said on Thursday that when he first met Mr Kelleher more than 30 years ago, the airline executive was about to deliver a speech at a New York hotel. "The manager asked that he refrain from smoking. Herb looked up, smiled, and said: 'No smokey, No talkey.'.”
New Jersey-born Mr Kelleher served as Southwest's executive chairman for 30 years until 2008.
He was chief executive from September 1981 to June 2001.
Steven Udvar-Hazy, executive chairman of Air Lease and another pioneer of the aircraft leasing industry paid tribute to Kelleher as “the builder of the worldâs most successful low fare airline”.
"Herb: a final Wild Turkey Bourbon toast from all of your closest friends," he added.
Mr Kelleher set up Southwest with Rollin King who died in 2014, aged 83.
