Near midair collision.

Attributes
ACN	96699
Time
Date	198810
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : ont
State Reference	CA
Altitude	msl bound lower : 10000 msl bound upper : 10500
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	descent : approach descent other
Route In Use	enroute : on vectors enroute airway : ont
Flight Plan	IFR
Aircraft 2
Operator	general aviation : personal
Make Model Name	Small Transport, Low Wing, 2 Recip Eng
Flight Phase	climbout : intermediate altitude
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	96699
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 110 flight time total : 6000 flight time type : 1000
ASRS Report	96907
Events
Anomaly	conflict : nmac
Independent Detector	other controllera other flight crewa
Resolutory Action	flight crew : took evasive action
Consequence	Other Other
Miss Distance	vertical : 350
Supplementary
Primary Problem	Flight Crew Human Performance

Narrative:

Large transport was heading 255 degree at 10000' MSL when pop-up traffic was called by an alert ontario approach controller. Traffic initially called at 1 O'clock, 5 miles passing 9800' in a climb. Visual acquired at 3 miles by the second officer. Aircraft appeared to be a twin. Low wing, single tail private. As a collision course appeared probable, large transport initiated a climb to 10,500' MSL as the aircraft passed 200-500' directly below us. The other aircraft took no evasive action and apparently did not see us. Weather--VMC on top of a smog layer approaching ontario airport (29 NM east). Thank heavens for engineers. He probably saved us. Sometimes an extra pair of eyes is unremarkable.

Original NASA ASRS Text

Title: NMAC.

Narrative: LGT WAS HEADING 255 DEG AT 10000' MSL WHEN POP-UP TFC WAS CALLED BY AN ALERT ONTARIO APPROACH CTLR. TFC INITIALLY CALLED AT 1 O'CLOCK, 5 MILES PASSING 9800' IN A CLIMB. VISUAL ACQUIRED AT 3 MILES BY THE S/O. ACFT APPEARED TO BE A TWIN. LOW WING, SINGLE TAIL PRIVATE. AS A COLLISION COURSE APPEARED PROBABLE, LGT INITIATED A CLIMB TO 10,500' MSL AS THE ACFT PASSED 200-500' DIRECTLY BELOW US. THE OTHER ACFT TOOK NO EVASIVE ACTION AND APPARENTLY DID NOT SEE US. WEATHER--VMC ON TOP OF A SMOG LAYER APPROACHING ONTARIO AIRPORT (29 NM EAST). THANK HEAVENS FOR ENGINEERS. HE PROBABLY SAVED US. SOMETIMES AN EXTRA PAIR OF EYES IS UNREMARKABLE.

Data retrieved from NASA's ASRS site as of August 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.