According to the FAA and NTSB, as well as from what I can see on the photos, the vertical stabilizer shows no sign of being hit by anything. If something struck it hard enough to break it off, it'd leave a lot of visible damage. The evidence just doesn't seem to support that scenario.

You're right that the vertical stabilizer and rudder might not fall in a straight ballistic path. However, keep in mind that each of these components is quite heavy, easily a few thousand pounds, so they wouldn't really flutter as they fell to the ground. The plane wasn't going very fast at the time, either, so the aerodynamic forces that would cause them to divert from a ballistic tragectory would be somewhat weaker than if it came apart at high speed. I suspect the eyewitnesses who claimed a wing broke off were really seeing the vertical stabilizer and rudder. To the best of my knowledge, the wings were still attached at impact.

Now that the investigation is deep into the analysis phase, we aren't getting the daily updates like we were last week. Here's the latest report (last Saturday) from Aviation Now.

CNN has some of the data recorder analysis summarized. Go to the page I linked and click on "Flight 587's final moments." There's also a map showing where the parts came down relative to one another. It appears the engines definitely came off well after the vertical stabilizer and rudder. There's also CNN's report on the final minute of the flight. This article contains a couple important pieces of info:

"There were no marks on the fin section or the rudder," NTSB member George Black told CNN earlier. "We haven't found any other evidence of any impact with any foreign object. It appears to be some sort of aerodynamic effect."

Haueter reported that examinations of both engines found no indication of pre-impact failure or fire and no evidence of a bird strike. Investigators have repeatedly said there are no signs of sabotage.

My comments on the FDR summary will be marked inside of brackets [].

Flight 587's final seconds

Information from the last 28 seconds of the flight data recorder aboard Flight 587 according to NTSB reports.

First wake, 28 seconds remaining

• Acceleration data is consistent with a wake encounter about 28 seconds before the end of the flight data recorder information. Airplane position did not change much in the first encounter (of a wake).

Second wake, 8 seconds remaining

• Measurements of forces on the aircraft are consistent with a wake encounter about 8 seconds before the end of the recording.

• The second wake encounter appears to be similar in intensity to the first. The airplane appears to be responding normally.

• Near the end of the second wake, the aircraft experiences sudden forces of 0.3 G, 0.4 G from one side and then 0.3 G force from the opposite direction.
The rudder moves in the opposite direction of the side forces.

[The FDR only records rudder position. It doesn't record control inputs. It's possible the copilot who was flying the plane overcorrected. There's also a possibility, perhaps a slim one, that there was some rudder flutter underway seeing as how the rudder moved in the opposite direction of the side forces. If it moved uncommanded, that could be flutter or perhaps a rudder actuator malfunction like what has happened on the Boeing 737.]

Last seconds

• About 2.5 seconds before the end of the recording, the rudder position data becomes unuseable.

[I believe the rudder has broken off at this point, probably along with the vertical stabilizer.]

• The side force increases from about 0.3 G to about 0.8 G (0.3 G and 0.4 G is considered to be a very significant force).

[This fits with the scenario I described in my earlier post. Without the vertical stabilizer, yaw axis rotation would rapidly increase as the plane quickly went out of control.]

• The airplane heading changes at about 10 degrees per second to the left.

[This also fits my scenario.]

• The bank angle is increasing through 25 degrees, left wing down, with the control wheel to the right.

[The rotation in the roll axis also fits my scenario due to roll/yaw coupling.]

• The nose of the plane drops to 30 degrees while the vertical G-load increases to over 2 Gs.

[As the bank angle and yaw angle increased, the plane probably fell off towards the ground completely out of control.]

• The end of the recording occurs when the airplane is at an altitude of 2,900 feet and 20 or more seconds before the cockpit voice recorder stopped.

[According to articles I read last week, the CVR had a small battery inside to provide backup power. Apparently, the FDR didn't. In several recent crashes, a loss of electrical power before impact has caused one or both recorders to stop. I suspect this happened on 587 when the engines broke from the plane. I've been wanting the airlines to put backup batteries in the CVRs and FDRs for several years now.

When the engineers are designing the engine pylons, the look at the loads they realistically expect the fixture to encounter and add in a 50% safety margin. I believe they never anticipated a yaw motion anywhere near as severe as 587 encountered simply because they never imagined the plane would lose the vertical stabilizer. Had the plane simply lost its rudder, it's possible the crew could've maintained control through differential thrust. That's what the crew of the Sioux City, IA crash did back in the late 1980s when a catastrophic failure of the DC-10's number 2 engine knocked out all hydraulics and left the rudder skewed about 10 degrees to one side.

However, losing the vertical stabilizer on 587 doomed the plane. There was simply no way that plane was flyable without the stabilizer. The million dollar question is why did it come off. Like I said before, there doesn't seem to be any sign of tampering or explosives. The potential impact to the airline industry is enormous if this crash indicates some sort of problem inherent to composite structures or the way they're repaired.]