Another Twilight Zone that William Shatner starred in was called, Nightmare at 20,000 Feet and is a classic Twilight Zone episode. Below is the Rod Serling introduction to this one.
Portrait of a frightened man: Mr. Robert Wilson, thirty-seven, husband, father, and salesman on sick leave. Mr. Wilson has just been discharged from a sanitarium where he spent the last six months recovering from a nervous breakdown, the onset of which took place on an evening not dissimilar to this one, on an airliner very much like the one in which Mr. Wilson is about to be flown home - the difference being that, on that evening half a year ago, Mr. Wilson's flight was terminated by the onslaught of his mental breakdown. Tonight, he's traveling all the way to his appointed destination, which, contrary to Mr. Wilson's plan, happens to be in the darkest corner of the Twilight Zone.
Here’s the entire Wikipedia entry: Nightmare at 20,000 Feet.
And here’s still from the show, that “Boris” has worked his Photoshop magic on! Another classic, “Boris,” thanks, Daddio!