Call of Duty 4: Modern Warfare is a first person shooter game that was developed by Infinity Ward and published by Activision in November 2007. The game, changed quite drastically in development with a substantial amount of cut content, far more than other games in the series. While these levels are rendered unplayable in the release builds, early builds have arisen with several of these cut levels fully playable, while others remain unavailable, indicating that they were cut earlier in development and never existed in a playable form. Footage of several of the cut levels was published by YouTube user UHDGaming in 2016 from an Xbox 360 pre-alpha build, but seemed reluctant to release the build to the public, or answer questions about the build. Two builds in particular are circulating on the Internet, builds 253, dated January 31st 2007, and 328, compiled a few months after.
It was originally planned that the training mission would have taken place with the USMC, as opposed to the SAS. The level retains many of the objectives that were seen within the FNG mission featured in the final game. The level is removed from the final build, with only the compass file and the strings file, (containing objectives, prompts to the player, and so on) being preserved. A fully playable version of the level is seen in the pre-alpha build. Seen in this level are several characters that didn't feature in the final game, as all missions containing them were removed, such as the playable character Michael Carver.
The original mission was longer than that seen in the final product. After finishing weapons training with Gaz, instead of going straight to Cpt. Price for the CQB course, the player would have had to first go to Sgt. Newcastle for explosives training, and then complete an obstacle course. These were cut so late in development, the obstacle course and explosives pit can be found in the final game, just with the objective triggers removed. They were restored as optional objectives as part of Modern Warfare Remastered.
The exact name of this level is unknown, but is given this name as the game's mod tools refer to the assets in the level with
cobrapilot. The level was referenced in some promotional material for the game, so was clearly cut quite late in development.  The level can be found fully playable in the pre-alpha build, with even button prompts, controller layouts and sound effects prepared for the level. (albeit, at this point in development, a bit crudely presented)