This article is from the Final-Fantasy and other Square Soft Games FAQ, by firstname.lastname@example.org (Nick Zitzmann) with numerous contributions by others.
Each stage in the game has three special bonuses which can be obtained.
Getting these special bonuses can unlock several hidden game features,
such as extra weapons and more Einhanders to fly.
Here's a rundown on how to get each special bonus:
* Shoot down every sign you see.
* Shoot down all of the armed craft before and after the signs. The
craft immediately following the signs will have a Riot.
* At the first mini-boss, destroy the bottom of the boss instead of the
head. (This is easier said than done.) After accomplishing this, you'll
take an alternative route to the end of the level.
* At the beginning level, destroy three gunpods to make a red gunpod
appear. Destroy the red gunpod for a bonus.
* At two parts in the level, the game's progression will halt in order
to take out armed trains. Each train generates turrets, and in order to
get the two bonuses, it is necessary to shoot down a certain number of
turrets. (8-10 of them?)
* Shoot down three spinning tops to make a red spinning top appear.
Destroy the red spinning top.
* During the battle with the walking cannon, shoot down a number of
vehicles to receive another bonus.
* After the walking cannon mini-boss, destroy the little aircraft
carrier. Then, destroy all the crafts that fall out of it.
* When fighting the submarine, destroy the submarine's body first.
Afterwards, destroy the command section.
* After defeating the level mini-boss, you'll enter a maze-like area.
Take the lowest route and stay there. Look for a strange-looking enemy.
* Destroying the ground before the stage boss will reveal a bonus. The
easiest way to do this, if you got the stage's second bonus, is to shoot
down (but not destroy) an enemy which appears here.
* Shoot down every moving platform just before the mini-boss.
* Do as much damage to the body parts of the mini-boss without
destroying it. (This is easier said than done!)
* Look for a red aircraft which appears just before the stage boss.
The "rocket and satellite" level:
* After disabling one of the thrusters, a red enemy may occasionally
appear on the screen. Shoot three of them for bonuses.
* Three red enemies appear in this level; shoot them for the bonuses.