Kate McWilliams, with budget carrier easyJet, is based at London's Gatwick Airport. She began flying at the age of 13 in the air cadets before embarking on a training programme at CTC Aviation in Southampton on her 19th birthday.
She first became interested in planes after attending an air show at age four.
The British carrier, easyJet believes McWilliams has become the world's youngest commercial airline captain -- with 19-year-old co-pilot Elsworth also one of the country's youngest co-pilots.
"I get asked how old I am on an almost daily basis...Usually, that question comes from the cabin crew but sometimes passengers ask too. When I tell them I'm 26, most people are impressed with my achievement at such a young age," she said.
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McWilliams joined easyJet in May 2011, as a first officer and recently took up the rank of captain after passing the airline's command course.
An easyJet spokeswoman said the Luton-based airline has carried out research which leads it to believe she is the youngest commercial airline captain in the world.
"With Gatwick having such an extensive route network my roster is very varied so I rarely fly to the same place twice in the same month," she said.
"I love being a commercial pilot for easyJet, and I am proud that I have now achieved my ambition of becoming a captain," she said.
The spokeswoman said the airline believes McWilliams is the world's youngest commercial airline captain.
Julie Westhorp, chairwoman of the British Women Pilots' Association (BWPA), said she hopes McWilliams' progression inspires more women to consider pursuing a career in aviation.