This video was part of newly released NIST videos following Freedom of Information Act requests by the International Center for 9/11 Studies.
From IC 9/11 Studies
The black plane comment by one of the firemen is also collaborated by the video "What We Saw" which documents a live viewing of the destruction of the WTC. A witness exclaims in that video at around 12:10 after the second impact, "It was a military plane."
A new Prison Planet article goes into more detail on other witnesses to the explosions.