The stockpile is a tab in the mercenary's PDA in Mercenaries 2: World in Flames in which the player can select vehicles, supply drops and airstrikes. Once you access it there are three other tabs to select: Airstrikes, Vehicles, and Supplies.
From the Airstrikes tab, you can call in:
- Artillery strikes
- Attacker jet bomb drops
- Missile strikes
From the Vehicles tab you can call Ewan to deliver vehicles, there are 5 different sub-categories:
- Light Military
- Heavy Military
From the supplies tab you can call in a Ewan to drop various supply drops.
- The more airstrike munitions the player accumulates in the stockpile, the more airstrikes will be seen inside the PMC, there seems to be a limit in the amount of displayed airstrikes inside the PMC (probably so that it can be completely stuffed with airstrike munitions).