Here is the full list of all 16 Flying Red Barrel - there are The Diary of a Little Aviator achievements.
Complete all achievements in Flying Red Barrel
Clear Stage 1
Clear Stage 2
Clear Stage 3
Clear Stage 4
Clear Stage 5
Clear the game without using any continues
Unlock 5 different endings
Unlock 10 different endings
Unlock all 18 different endings
Defeat Blue Crow the 2nd
Defeat Flying Castle's main cannon
Reach maximum Bonus multiplier
Gain 1 Million score
Terrorize the Seagulls in Stage 1
Defeat the Secret Bat Boss