Wikipedia:

"Murder On Flight 502 is a 1975 American made-for-TV movie directed by George McCowan and starring Robert Stack, Farrah Fawcett-Majors, Sonny Bono, Danny Bonaduce, and Fernando Lamas.

"After a Boeing 747-100 takes off from New York City to London, a mysterious note turns up at the airport stating that passengers aboard the flight will be killed before the Boeing 747-100 lands at Heathrow. This creates a twist on the classic whodunit suspense format that may be described as "Who's going to do it to whom?" ΓÇö as all of the quirky passengers seem like potential culprits and/or victims. At first the note is brushed off as a prank, but the plot thickens considerably once passengers do begin turning up murdered."
 
http://en.wikipedia.org/wiki/Murder_on_Flight_502
www.imdb.com/title/tt0073418/