Narrative:

My aircraft was in level cruise, heading 270 degrees, altitude 10500', VFR flight west/O a flight plan in excellent VFR conditions. I was squawking 1200 on my transponder and was emitting a mode C altitude code. At a point approximately 45 mi southeast of ord I was overtaken extremely close abeam on the right side by a large commercial (perhaps corp) twin jet aircraft in level flight at the same altitude and heading. Because of speed differential of at least 150 KTS, and the aspect of the aircraft (tail-on immediately after passing), I was unable to positively identify the aircraft type. The aircraft appeared to be of medium large transport confign, was mostly aluminum in finish with (I believe) some red trim. (It was not an air carrier X aircraft.) the aircraft continued in level flight on a parallel course until it disappeared out of sight straight ahead after several seconds. The aircraft at no time attempted to maneuver. Because of the rapid closing speed, and the approach directly from the rear, neither I nor my passenger observed the overtaking aircraft until it was directly abeam, at which time it appeared to completely fill the side window. Clearly, neither pilot of the other aircraft observed my aircraft prior to passing directly abeam, and probably didn't observe me even as it passed. It is highly likely, though, that passenger in the aircraft would have observed the near miss. I'm not familiar with scheduled airline procedures, but it must be assumed that the aircraft was not under positive control or the controller would have observed my aircraft on his radar and warned the approaching pilot. It should be noted that the sun was not a factor, since the jet was approaching my aircraft on a down-sun course.

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Original NASA ASRS Text

Title: CLOSE PROX GA SMA IN CRUISE AT 10500' ON AIRWAY AND ACR MLG CLIMBING OUT OF ORD.

Narrative: MY ACFT WAS IN LEVEL CRUISE, HDG 270 DEGS, ALT 10500', VFR FLT W/O A FLT PLAN IN EXCELLENT VFR CONDITIONS. I WAS SQUAWKING 1200 ON MY XPONDER AND WAS EMITTING A MODE C ALT CODE. AT A POINT APPROX 45 MI SE OF ORD I WAS OVERTAKEN EXTREMELY CLOSE ABEAM ON THE RIGHT SIDE BY A LARGE COMMERCIAL (PERHAPS CORP) TWIN JET ACFT IN LEVEL FLT AT THE SAME ALT AND HDG. BECAUSE OF SPD DIFFERENTIAL OF AT LEAST 150 KTS, AND THE ASPECT OF THE ACFT (TAIL-ON IMMEDIATELY AFTER PASSING), I WAS UNABLE TO POSITIVELY IDENT THE ACFT TYPE. THE ACFT APPEARED TO BE OF MLG CONFIGN, WAS MOSTLY ALUMINUM IN FINISH WITH (I BELIEVE) SOME RED TRIM. (IT WAS NOT AN ACR X ACFT.) THE ACFT CONTINUED IN LEVEL FLT ON A PARALLEL COURSE UNTIL IT DISAPPEARED OUT OF SIGHT STRAIGHT AHEAD AFTER SEVERAL SECS. THE ACFT AT NO TIME ATTEMPTED TO MANEUVER. BECAUSE OF THE RAPID CLOSING SPD, AND THE APCH DIRECTLY FROM THE REAR, NEITHER I NOR MY PAX OBSERVED THE OVERTAKING ACFT UNTIL IT WAS DIRECTLY ABEAM, AT WHICH TIME IT APPEARED TO COMPLETELY FILL THE SIDE WINDOW. CLEARLY, NEITHER PLT OF THE OTHER ACFT OBSERVED MY ACFT PRIOR TO PASSING DIRECTLY ABEAM, AND PROBABLY DIDN'T OBSERVE ME EVEN AS IT PASSED. IT IS HIGHLY LIKELY, THOUGH, THAT PAX IN THE ACFT WOULD HAVE OBSERVED THE NEAR MISS. I'M NOT FAMILIAR WITH SCHEDULED AIRLINE PROCS, BUT IT MUST BE ASSUMED THAT THE ACFT WAS NOT UNDER POSITIVE CTL OR THE CTLR WOULD HAVE OBSERVED MY ACFT ON HIS RADAR AND WARNED THE APCHING PLT. IT SHOULD BE NOTED THAT THE SUN WAS NOT A FACTOR, SINCE THE JET WAS APCHING MY ACFT ON A DOWN-SUN COURSE.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.