U.S.A. Air Force General, Stealth Fighters with Aircraft Ammo upgrade. Why...? Options

[LeBrute]

When using the USA Air Force General's Stealth Fighters against a base defense (let's just say a vanilla Patriot), it takes two of the units (without any upgrades) to fully destroy it in one run. After the Aircraft Ammo upgrade is purchased, Stealth Fighters receive two additional missiles, thus, doubling their payload. Shouldn't a doubled payload mean doubled damage?

Why is it, then, that, even after receiving the Aircraft Ammo upgrade and Laser-Guided Missiles upgrade and Bombardment Strategy, one Stealth Fighter is not enough to deny a Patriot? Why does it still take two of them to fully knock one down? If the unit is given twice the amount of missiles, shouldn't it deal twice the amount of damage and be just as effective as two individual Stealth Fighters (especially after receiving additional damage-boosting upgrades)?

Just curious why is doesn't work like that.

Thank you.