Death in the Clouds

A standard mystery plot: someone is murdered on a passenger flight while it is in the air. From a writer's perspective, this has the advantage of providing both a closed setting and a limited suspect pool without either feeling overly contrived. These days it also provides the additional puzzle of how the killer smuggled a weapon on board.

The detective can either be on the flight or brought in once the plane has landed.

The successor to Thriller on the Express (though it still gets used in non-modern settings).

As a Death Trope, Spoilers ahead may be unmarked. Beware.

Examples of Death in the Clouds include:

Anime and Manga

Used in Detective Conan Shinichi's first case and Movie 8 both feature this.

Comic Books

Occurred in one issue of The Maze Agency ("The Mile High Corpse" ).

Film

Fugitive in the Sky
Sky Murder, a 1940 Nick Carter film
The Falcon in Danger.
A variant occurs in Snakes on a Plane, though the heroes figure out that the Big Bad would be just as happy bringing down the entire plane.
The 2005 film Flight Plan is a variant of this plot, although with a kidnapping instead of a murder.

Literature

The Trope Namer is the Agatha Christie novel Death in the Clouds first published in 1935 (called "Death in the Air" in the USA). This might also be the Trope Maker.
The disappearance (and apparent murder) of his wife and daughter from a plane in flight over lake Ontario in Justice, Inc. delivers the shock that transforms Richard Benson into The Avenger.
The Usbourne Puzzle Adventure: Murder on the Midnight Plane.

Live Action TV

CSI - "Unfriendly Skies"
CSI: Miami - "Flight Risk"
CSI New York - "Turbulence"
A twisted version - House needs to find out if a man vomiting with sores and severe headaches is suffering from meningitis, or something else. If it's the former, they're all dead. He's got something, but everyone else just has mass hysteria.
In an episode of Bones where they're taking a plane to China a dead body is found, and they have to discover and arrest the murderer before they touch down or else the case becomes "property" of China.
Played with in "Mr. Monk and the Airplane". The actual murder occurred in the airport, but Monk was on the plane with the murderer and only had as long as the flight lasted to solve the crime.
- Actually, there WAS a murder on the plane. The flight attendant got rid of the evidence (unknowingly, though.)
A variation appears in—of all places—the Supernatural episode "Phantom Traveler", where a demon's been causing plane crashes and the brothers have to find out who it's possessing and exorcise it, before it crashes another plane. Unfortunately, they don't manage to stop it getting on the plane, so the climax takes place on a plane. This was the first episode of the show to feature demons.
Another variation from Leverage, "The Mile High Job", where someone on the plane has evidence they plan to destroy before it can be used against their company in court. The "evidence" turns out to be another employee, who the company wants assassinated before she can testify. And just to be certain, the company try to bring down the whole plane...
NCIS has the episode "Jet Lag", which started out as "keep the federal witness from getting murdered" but added "find out who killed that flight's Air Marshall" to the to-do-before-the-flight-lands list.
- The Pilot episode, "Yankee White" is also one of these.
  - To be specific, the murder occurs on air force one—which adds the question of how someone managed to kill someone with secret service all over the place. But considering that they let the President have ribs from a local restaurant without testing them...
Parodied in a Saturday Night Live sketch featuring Sir Ian McKellen as a Sherlock Holmes Expy who solves a murder aboard a hot air balloon.
The John Doe episode "Manifest Destiny".
Taken a step beyond the clouds in the 1985 series Murder In Space. The crew of an international space mission are on the return leg from Mars to Earth when an explosion occurs on the craft Conestoga, shortly after the murders start. The crew of the returning craft are forbidden to return until the murderer is caught.
The pilot episode of Fringe has an airplane land with everyone on board dead from a biological weapon. They then have to figure out how the weapon got on board, why, where it came from, and is there more of it.
Murder, She Wrote: "The Corpse Flew First Class"

Radio

Occurs Cabin Pressure.

Video Games

Ace Attorney Investigations has one of these.

Real Life

Carlos Pizarro, former guerrilla member and colombian presidential candidate, was murdered on a plane in April 1990. A weapon was concealed in the bathroom of the plane, and a hired thug shot him at point-blank range. He was then taken down by a security agent. Paramilitary leader Carlos Castaño said later that he had planned the crime. During that same campaign, two other candidates were also killed.