The tourists' return flight from Rome back to New York is TWA flight 841. On September 8, 1974, TWA flight 841 crashed into the Ionian Sea en route from Athens to Rome (full scheduled route: Tel Aviv - Athens - Rome - New York). The plane was destroyed by a bomb hidden in the cargo hold, which caused structural failure resulting in uncontrollable flight. This was the first known instance of a young Arab boarding an American plane in a suicide mission.
During one of the interludes that Shelly Ferguson (Hilarie Thompson) spends with the free-spirited Bo (Luke Halpin), she admires the slogan "Suppose They Gave a War and Nobody Came" that he has displayed on his motorcycle. That phrase is also the title of the next (and last) movie--Suppose They Gave a War and Nobody Came? (1970)--in which their co-star, Pamela Britton, appeared before her untimely death in 1974.
One of the subplots involves Fred and Edna Ferguson who take their 19-year-old daughter Shelly on the tour to get her away from her boyfriend in the US. On the trip she falls for an intriguing student radical called Bo who organizes protests across Europe. Edna is played by Peggy Cass, who was also a regular panelist on various TV shows in from the 1960s-1980s, including the popular To Tell the Truth (1956) in its heyday. Bo is played by Luke Halpin. who became famous in the early/mid-'60s as the star of two movies and the TV series Flipper (1964) playing Sandy Ricks. Luke's rising fame saw him appear as a 'contestant' on "To Tell the Truth" in March 1964 just before he turned 17. Peggy Cass was one of the four panelists who quizzed Luke (and the two other impostors) in an attempt to determine the real Luke Halpin. She was the only one of the four to make a wrong choice.