28Mar2006 [Revised 8Apr2009]

The Smoking Plane

The official* impact time of United Flight 93 is 10:03:11 AM.

A “report of black smoke” was made “about 1 minute 37 seconds after the [official] impact time of United 93,” that is, at about 10:04:48 AM, from an Air National Guard plane in the area.

But a seismic report determined that the impact of United Flight 93 with the ground was at 10:06:05 AM plus or minus 5 seconds. If the seismic data are correct, then the black smoke of Flight 93’s demise was reported while Flight 93 was still airborne.

The controversy regarding the precise “impact time” has great importance to the question of whether Flight 93 was destroyed while airborne or whether it was deliberately crashed by the hijackers, as the 9/11 Commission speculates. Although other possible fates of Flight 93 exist, only these two are considered here.

The 9/11 Commission Report [July 2004, page 30]

United 93 crashed in Pennsylvania at 10:03:11, 125 miles from Washington, D.C. The precise crash time has been the subject of some dispute. The 10:03:11 impact time is supported by previous National Transportation Safety Board analysis and by evidence from the Commission staff’s analysis of radar, the flight data recorder, the cockpit voice recorder, infrared satellite data, and air traffic control transmissions. 168

Five minutes later, the Command Center forwarded this update to headquarters:

Command Center: There is a report of black smoke in the last position I gave you, fifteen miles south of Johnstown.

FAA Headquarters: From the airplane or from the ground? Command Center: Uh, they’re speculating it’s from the aircraft. FAA Headquarters: Okay.

Command Center: Uh, who, it hit the ground. That’s what they’re speculating, that’s speculation only. 169

The aircraft that spotted the “black smoke” was the same unarmed Air National Guard cargo plane that had seen American 77 crash into the Pentagon 27 minutes earlier. It had resumed its flight to Minnesota and saw the smoke from the crash of United 93, less than two minutes after the plane went down. 170

The 9/11 Commission Report [endnote #170, page 462]

170. . . . For communication regarding “black smoke,” see FAA memo, “Full Transcript; Aircraft Accident; N591UA (UAL93) Somerset, PA; September 11, 2001,” May 10, 2002, pp. 16–18 (Cleveland Center, Imperial Radar position). This report from the C-130H was recorded on ATC audio about 1 minute and 37 seconds after the impact time of United 93 as established by NTSB and Commission analysis of FDR, CVR, radar, and impact data sets — more than a minute before the earliest impact time originally posited by the authors of the seismic data report. [Note: The authors of the seismic report posited only one time, 10:06:05±5, no others.]

The 9/11 Commission Report [endnote #168, pages 461-462]

168. . . . We also reviewed a report regarding seismic observations on September 11, 2001, whose authors conclude that the impact time of United 93 was “10:06:05±5 (EDT).” Won-Young Kim and G. R. Baum, “Seismic Observations during September 11, 2001, Terrorist Attack,” spring 2002 (report to the Maryland Department of Natural Resources). But the seismic data on which they based this estimate are far too weak in signal-to-noise ratio and far too speculative in terms of signal source to be used as a means of contradicting the impact time established by the very accurate combination of FDR, CVR, ATC, radar, and impact site data sets. These data sets constrain United 93’s impact time to within 1 second, are airplane- and crash-site specific, and are based on time codes automatically recorded in the ATC audiotapes for the FAA centers and correlated with each data set in a process internationally accepted within the aviation accident investigation community. Furthermore, one of the study’s principal authors now concedes that “seismic data is not definitive for the impact of UA 93.” Email from Won-Young Kim to the Commission, “Re: UA Flight 93,” July 7, 2004; see also Won-Young Kim, “Seismic Observations for UA Flight 93 Crash near Shanksville, Pennsylvania during September 11, 2001,” July 5, 2004.

Compare excerpts from the original study, “Seismic Observations during September 11, 2001, Terrorist Attack,” below. Please note that “not definitive” evidence can still be the very best that is available. There is no seismic evidence to support the official impact time (into the ground) of 10:03:11, a fact Dr. Kim confirmed to the Commission in his subsequent report of July 5, 2004. “For the origin time #1, 10:03:10.9, there are no discernable [sic] seismic siganls [sic] to associate with the UA Flight 93 crash.” OVER