This film falls firmly in the So Bad You'll Love It.
After a plane takes off for London, a note is found in the airport saying that some people are going to be killed.
And it is not long after that, that someone is killed.
The captain (Robert Stack) tries to keep the passengers calm while the people on the ground do background checks on everyone and they learn that some of the passengers have history with one another. But it seems that there's a lot more going on.