When Sky Liner came out in 1949 this was Lippert Pictures trying to take advantage of current headlines involving espionage in the State Department. Joe McCarthy was a year away from his famous accusations in Wheeling, West Virginia about the Communists in government. But in 1949 Secretary Of State Dean Acheson was defending himself against right wing attacks about the Red Menace invading our State Department. Also remember that the Hiss case was coming to a head as well.
So what we have in Sky Liner is spy Rochelle Hudson, secretary to a State Department bigwig apparently ready to defect. A Communist takes her boss's place after killing him and the two are on the way to a conference. You have to believe there's going to be a defection because once they discover the real boss's body, it's all over. And that's supposing no one at the conference will realize there's a phony planted among the delegates.
Never fear because the FBI in the person of Richard Travis has her in his sights for a while and he also might get a twofer because foreign agent Stephen Bekassy is also on this transcontinental flight. It turns out as films in this era always did with the FBI protecting us from Red secretaries.
Sky Liner is one of the dumbest films from the Cold War I've ever seen and one of the dumbest from Lippert studios. And that is going some.