Mommy...

"Mommy, Mommy, Mommy MOMMY (the sound of Bubba coming down the hall way), what comes out of the back of these holes (pointing to the jet engines on the back of his toy plane)?"

Mommy pauses a moment... "FIRE"

"OH SWEET, boys FIRE comes out of these, that is so COOL!"

Yes, Bubba, so cool.

While I know that technically that is not the right answer, it is the answer I knew he would understand and LIKE.