when analyzing 911, one must consider the 6/21/01 eclipse on the solstice as it was the primary setup for the energy that would play out. aside from the obvious overall setup of the 6/21/01 chart (strong focus on the 11th/uranus, as well as the 5/11 polarity), it has SU/MA=JU/CH at tight orb, which I dont think many people have paid attention to. quite the combination there, especially when present on an eclipse, not to mention an eclipse on the aries point degree!
moon was trigger finger, with the moon/(mean)north node midpoint exactly on the 6/21 eclipse degree, with moon exactly squaring the chiron/north-node midpoint and conjuncting (by 5 arcmin) the jupiter/saturn midpoint. this activated not only the 6/21 eclipse, but the jupiter/saturn cycle, which had its last conjunction on the DC midheaven in taurus.
the major simple transit between 6/21 and 9/11 was 9/11 mars opposing the 6/21 eclipse, and 9/11 sun squaring 6/21 mars. orbs are a little wide on these (about 1.5 degrees) but still close in a relative sense for a direct (non-midpoint) transit. the other kicker was the sun t-squaring the saturn/pluto opposition.. again, fairly wide orbs but still within "spec" - one can allow a bit of extra orb for the powerful sun anyways, especially with powerful low-harmonic aspects like the square.
also, at impact, chiron squared the mars/saturn midpoint (2 arcmins), and the sun opposed the saturn/chiron midpoint (3 arcmins) [these are both transiting midpoints on 911]
6/21:
its also worth considering the retrograde dance mars had with pluto, chiron, and pallas.. mars triple conjuncted with pluto/pallas, continued to chiron, where both mars and chiron stationed retrograde together. mars then backtracked to almost hitting pluto again, then stationed direct to go over chiron again... mars makes it to an applying 1'40 conjunction with the south node (a bit past chiron), in opposition to the eclipse, on 911.
the lillith/uranus conjunction on the 6/21 eclipse seems very powerful, as well. uranus is in a tension ruler position over the massive 5/11 polarity buildup, and any conjunction to a tension ruler is very important.
... just some interesting observations about 911 that don't seem to be widely mentioned. cheers