[Boudica]

Title isn't as good as "Snakes on a Plane" but you get the point.

Code:

A Boeing 747 cargo jet has been forced to turn around, after a horse escaped from its stall and caused chaos as the plane cruised at 30,000ft (9,144m).

The plane was headed to Belgium from New York but did a U-turn roughly 90 minutes after its departure when the animal got loose.

Air traffic control audio recorded the pilot saying: "We have a live animal, a horse, on board the airplane. The horse managed to escape."
"We cannot get the horse back secured."

Source

Man phones wife: Sorry honey, I'm going to be late coming home, the plane had to turn back around.
Wife: Why?
Man: Have you heard the horse escaping? It’s a terrible tale of WHOA!

Spoiler:

That joke hurt me more writing it than it hurt you reading it.