When Sonic is in the air you do have limited control over him as you can make him move left or right slightly by pressing the appropriate button. But by pressing down you can also stop Sonic from rising in mid air, this can be especially handy if you need to get onto a platform or slow your ascent for some reason. Pressing down at the start of level 2 will leave you in the cannon effectively giving you one free shot at the door in that room.
From the Options screen press the following buttons in this order: A, Down, B, Down, C, Down, A, B, Up, A, C, Up, B, C, Up.
To activate you then have to hold A and press Start for level 2, hold B and press Start for level 3, or hold C and press Start for level 4.