I'm new here so please forgive if this topic is redundant.

Initially I thought the conspiracy theorists were full of it, but what has never made sense to me is this:

Before the Pentagon outer wall collapsed, the hole from the initial impact of whatever, was less than 20 feet across. How can the exterior of the Pentagon show no damage from the two 12,000 pound jet engines (that are about 40 feet apart from each other on either side of the fuselage) slamming into the building at 400+MPH?

Is there an official explanation for this?

Thank you.