When airliners were first introduced in the 1930s, the stewardesses (most were women at that time) were required to be registered nursess, but that requirement was relaxed over the years as airline travel became more common.
The primary responsibility of the job is the safety of the passengers, but most of the work is customer service, serving meals and drinks and accommodating the individual needs of passengers. These roles sometimes conflict, as when flight attendants must cut off drinks for a passenger who has had too much, or force passengers to fasten seat belts, sit down, or otherwise follow safe procedures.
Particularly in the 1960s and 1970s the airlines contributed to confusion about these roles by advertising the attractiveness and friendliness of the stewardesses. One airline used named pictures stewardesses with captions like "I'm Kristin. Fly me." Another airline had the stewardesses changing clothes during the flight, wearing one garment while greeting passengers and another for serving meals. This practice was advertised as "the air strip" with accompanying bump-and-grind music. A policy of at least one airline required that only unmarried women could be flight attendants.
The 1967 book Coffee, Tea, or Me?: The Uninhibited Memoirs of Two Airline Stewardesses by Trudy Baker and Rachel Jones emphasized this aspect of the role. In fact, given the relative affluence of airline passengers and the presence of attractive young women, many marriages and other relationships undoubtedly began on planes.
Airlines were accustomed to taking women off the job after years of experience if they were deemed too old or unattractive, but a decision of the National Labor Relations Board ended that practice and recognized the professionalism of the job. [When did that ruling happen?] By the end of the 1970s, airlines called them "flight attendants".
The role of flight attendants received heightened prominence after the September 11, 2001 terrorist attack when flight attendants actively attempted to protect passengers from assault and also provided vital information to air traffic controllers on the attacks. This led to added security responsibilities for flight attendants.