How was there even an explosion at Shanksville? (officially speaking)

Before you start spouting ridicule at this notion, remember we are supposed to be basing things off the official story.

There was supposedly a large explosion when UA93 supposedly crashed in the grassy Shanksville field. It supposedly burned a section of the forest next to the crater and formed a huge mushroom cloud that was allegedly photographed by Val McClatchey in a single photo before "dropping her camera" and this large grey "plane crash" smoke cloud (grey?!) was recently "confirmed" by the newly released Dave Berkebile smoke cloud video that the media supposedly "wasn't interested in" right after 9/11.

(Top: McClatchey photo; Bottom: Berkebile video)

But if you look at the official story of how UA93 supposedly crashed, I'm wondering how was there even an explosion at all?!?


Remember, we are being told that this is how the Boeing 757 supposedly crashed:

Wally Miller: "The explanation was... The right wing hit the ground right there were the impact area is and as that happened, it took the front end...[does cartwheel hand gesture].

The front 1/3 of the plane, including the cockpit, slammed into the ground off of the wing and the front 1/3 broke off and flew up into the trees and there was a fireball behind it and the remaining 2/3'rds went down in the ground."

One of the landowners working with the FBI during the excavation described that the 757 went in the ground so fast that it didn't have a chance to burn:

The location was eventually determined because of some disturbed ground in front of a grove of charred evergreens, explains Jamie. The ground had swallowed up much of the wreckage.

Because of their familiarity with the property, the Svonavecs were asked to work with the F.B.I. on recovery efforts. “We hired some extra people and worked one long shift, seven days a week,” says Jim, a former federal mining inspector.

Using a Kobelco excavator, the process was slow and meticulous because “every bucket of material that was excavated went through screens,” explains Sally. Screening helped locate many body fragments and debris from the plane.

The plane “went in the ground so fast it didn’t have a chance to burn,” says Jim.

And you can see that there is hardly any fire damage to the grassy field surrounding the crater:

The only real fire damage seen is to the small section of forest next to the crater that the broken off cockpit section of UA93 supposedly flung into:

But as I've asked before, what's contained in the cockpit section of a 757 that could even cause an explosion?

So help me out here, based on the official story, how could there have been any explosion, no less a large one that supposedly produced a super huge grey mushroom cloud (grey?!) as seen the the McClatchey photo and Berkebile video?