How does 'Mile High Club' fit into the greater plot of the Modern Warfare franchise?

The epilog of Call of Duty 4: Modern Warfare (2007/2016) features a counter-terrorist hostage-rescue operation aboard an airliner, all while under severe time pressure.

This mission has remarkably little context compared to the expansive campaigns and characters in the rest of the Modern Warfare franchise. The theme of the mission is replicated in Modern Warfare 3's mission 'Turbulence'. Apart from that, there's no clear relation to the rest of the series.

How does 'Mile High Club' fit into the greater plot of Modern Warfare?

Solution 1:

According to this Call of Duty Wiki page, it... doesn't.

Sadly, it's just a bonus mission. You play the part of a nameless Task Force 141 operative, tasked with rescuing a hostage in a set amount of time. It is unrelated to the story entirely, and field journals obtained in the Hardened edition of Call of Duty: Modern Warfare 3 indicate that it took place prior to the events of Modern Warfare 2.

There is plenty of speculation about this mission, however. It has been confirmed that this mission is technically cut content, and was meant to be played after the first mission, which explains why the voice of Gaz is heard.

despite him dying in the game's story, shortly before Mile High Club becomes playable.