The "invincible aircraft" setting is available in the 
controls. When this is on,  pressing control-tab will add 
500 feet to your altitude. While in flight (or after you 
die), you can hit + s to go into slow mode. You start out 
in the exact geographic center of the island. No hit + x to
turn on your joystick. Now, you can move (point)with your 
stick. Here are the keys:

                  8 -- hit _ repeatedly _ to go forward
                  2 -- hit _ repeatedly _ to go backwards
                  4 -- hit _ repeatedly _ to go left
                  6 -- hit _ repeatedly _ to go right
                  7 -- hit _ repeatedly _ to go up
                  1 -- hit _ repeatedly _ to go down

The trigger fires the cannon (toned-down for some reason)
and fires heavily toned-down mavericks.
Now you can visit the baseball field in Havana, the hole 
in the wall, or complete the mission after you die.