Let's attack passive-aggressively. I'll get really mad at the aliens and then take it out on my wife. You vent your frustrations by picking fights bars. Ready? Okay, let's do this!
It's a bomber flying in and dropping bombs, the same effects are heard in the first stage when a bomber indeed flies in and dumps a couple napalm missiles on you which ignite a whole city block and cause exploding fireballs to bounce in and out of the inferno and stuff.
What, you didn't like the freeway level with the gigantic spinning alien-thing? Sir!
Contra 3 was a really solid game and a helluva lot of fun. I should break out the Super Famicom and slam through it again . . . good times, good times.