Unlockable: New Game SP
To unlock a new game feature (called New Game SP), simply complete the game once on a difficulty setting of your choice.
Unlockable: Expert Difficulty
To unlock expert difficulty, complete the game once.
Unlockable: Ace of Aces
To unlock a new game feature (called Ace of Aces), simply complete the game on normal difficulty or hard difficulty.
You can unlock each plane in the game, save the two most powerful, by clearing the game once through on Normal difficulty. The two strongest craft are thereafter unlocked by completing the game on Hard and Expert difficulties.
Below are a list of planes that can be unlocked in Normal difficulty. Simply defeat the mission listed for the corresponding planes.
Default - F-16C Fighting Falcon
Mission 4 - A-10-2 Thunderbolt / Mirage 2000
Mission 5 - Panavia Tornado
Mission 6 - F-14D Tomcat / F-2A / FA-18 Super Hornet
Mission 8 - Sukhoi 33 Flanker
Mission 9 - F-15E Strike Eagle / Rafale M
Mission 10 - F-117 Nighthawk
Mission 12 - EU Typhoon
Mission 13 - F22A Raptor / Sukhoi 47 Berkut
Unlockable: New Paint Schemes
Here's how you unlock new paint schemes. Complete the game once through on Normal mode, and unlock the Estovokian scheme. A third paint scheme can be unlocked by shooting down the enemy aces found only in Expert and Ace difficulty modes.
Unlockable: SP GamerPicture
To unlock SP GamerPicture, beat the game once through on Ace Difficulty.
Unlockable: Ace Difficulty
To unlock Ace Difficulty, beat the game once through on Expert Difficulty.
Unlockable: CFA 44 Nosferatu
To purchase the CFA 44 Nosferatu Fighter, you must first beat the game on Hard difficulty (or higher). After beating the game on that setting, you can purchase the plane for $230,000.