Jane Fonda has been quoted as stating that this film was the first time she enjoyed making a movie or thought she was any good at acting.
The New York production of the play "Sunday in New York" by Norman Krasna opened at the Cort Theater in New York on November 27, 1961 and ran for 188 performances. The original Broadway cast included a young Robert Redford.
Despite signs that read Idlewild International Airport, the airport scenes were filmed at the clearly recognizable Los Angeles International Airport, including the long corridor of mosaic tile that Cliff Robertson runs down and - reflected in a window of a door when Robertson leaves the terminal and walks downstairs to the tarmac - the famous Theme Building. At the time, TWA's Los Angeles hub had a dedicated office that assisted TV, commercial and film production at LAX. As a result, most airport scenes feature TWA as the airline. A notable exception is Bullitt (1968), which was filmed at SFO, hub to Pan Am and PSA.
The advertising for the film named the three-star line-up as Cliff Robertson, Jane Fonda, Rod Taylor - in that order - but the film's opening credits list Taylor first, Fonda, and then Robertson. Also of note, Fonda has a much larger role than either of her two leading men.