December 8, 1972
Chicago, Illinois
United Air Lines, Flight 553
Boeing B-737-222
N9031U
The aircraft crashed while making a non-precision instrument approach to Runway 31L. The
accident occurred in a residential area approximately 1.5 miles southeast of the approach end
of Runway 31L. Upon reaching minimum descent altitude, the pilot raised the nose of the
aircraft to stop the descent. The stall warning horn sounded and continued to sound until the
plane crashed 17 seconds later. The aircraft was destroyed by impact and subsequent fire.
Forty-three of 61 aboard killed.
RDO - Radio transmission from accident aircraft
CAM 1 - Voice identified as Captain
CAM 2 - Voice identified as First Officer
CAM 3 - Voice identified as Second officer
? - Unidentifiable voice
CHI APC = Chicago Approach
MTWR = Chicago-Midway Tower
* - Unintelligible word
# - Expletive deleted
() - Questionable text
9VS = Aero Commander 690, N309VS pilot
| 20.25:25.0 | CHI APC | Five five three, call the tower on one eighteen seven |
| 20.25:28.0 | RDO-2 | Eighteen seven, five five three |
| 20.25:35.5 | RDO-2 | Midway tower, United five five three, an' we're out of three for two |
| 20.25:39.0 | MTWR | United five five three, report passing the outer marker, number two on the approach |
| 20.25:41.0 | CAM-3 | Chicago, this is five five three (2nd officer calling ARINC) |
| 20.25:44.0 | RDO-2 | Okay, report the outer marker |
| 20.25:46.5 | CAM-1 | Let's have the gear down please |
| 20.25:48.0 | RDO-1 | [Start of first sound of first series off outer marker beacon tones] |
| 20.25:50.97 | CAM-3 | Chicago, five five three (2nd officer calling ARINC) |
| 20.25:51.62 | CAM | [Sound of a click - sound similar to sound of landing gear handle going into down detent] |
| CAM | [Sound of chime - simultaneous with click above] | |
| 20.25:52.20 | MTWR | Nine Victor Sugar, what's your airspeed? |
| 20.25:54.5 | [End sound of first series of outer marker beacon tones] | |
| 20.25:54.74 | 9VS | Ah, we're down to ah, hundred twenty knots |
| 20.25:55.06 | CAM | [Increase in ambient noise level - similar to increase made by nose landing gear extended] |
| 20.25:56.82 | MTWR | Ah hundred and twenty, okay |
| 20.26:00.64 | CAM | [Sound of first of four clicks in rapid increase - sounds similar to flap lever moved from 15 degrees to 25 degrees position] |
| 20.26:01.50 | CAM-? | Gear 'own |
| CAM | [Sound of several clicks - similar to sound of stabilizer trim actuation] | |
| 20.26:10.02 | RDO-1 | [Sound of beginning of second series of outer marker beacon tones] |
| 20.26:20.02 | RDO-1 | [End of sound of second series of outer marker beacon tones] |
| 20.26:24.66 | CAM-1 | Final descent check |
| 20.26:25.66 | CAM-3 | Flight and nav |
| 20.26:27.11 | CAM-2 | Cross-checked |
| CAM-? | * * | |
| CAM | [Sound of clicks - similar to sound of stabilizer trim actuation] | |
| 20.26:30.62 | RDO-2 | United five five three, an, ah Kedzie inbound |
| 20.26:35.97 | CAM-? | Flight |
| 20.26:36.38 | MTWR | United five five three, continue inbound, you're number two on the approach --I'll keep you advised. |
| 20.26:40.10 | CAM | [Sound of several clicks - similar to sound of electrical stabilizer trim actuation] |
| 20.26:40.47 | RDO-2 | Okay |
| 20.26:40.96 | CAM-2 | Cross-checked |
| CAM-3 | With a glideslope flag | |
| CAM-2 | No glideslope | |
| 20.26:41.10 | 9VS | Eh, nine VS has the runway |
| 20.26:43.06 | MTWR | Nine VS, runway three one left cleared to land |
| 20.26:44.67 | CAM-3 | Ah the --- landing gear |
| 20.26:46.18 | 9VS | Okay |
| 20.26:48.40 | MTWR | Nine VS, do ya have the right runway in sight by any chance? |
| 20.26:50.41 | CAM-2 | Down, three greens |
| 20.26:51.37 | CAM-3 | Speed brake? |
| 20.26:51.37 | 9VS | Affirmative |
| 20.26:52.45 | CAM-2 | Ah --- armed |
| 20.26:52.6 | MTWR | would you swing over to that and land? There's a jet about two m-- and disregard that, ah, okay, I see ya now, you're cleared to land on thirty-one left |
| 20.26:54.69 | CAM | [Sound of click - similar to sound made by moving speed brake lever to armed position] |
| 20.26:56.04 | CAM-3 | Wing flaps |
| 20.26:58.75 | CAM | [Sound of click - similar to sound made by flap lever moving into detent] |
| 20.26:59.42 | CAM-2 | Thirty, green light, pressure fluid. |
| 20.27:01.48 | CAM-3 | An the auto-pilot? |
| CAM | [Sound of click - similar to electrical stabilizer trim actuation] | |
| 20.27:02.96 | CAM-2 | Disarmed |
| 20.27:04.11 | CAM-2 | Ah thousand feet |
| 20.27:04.50 | MTWR | United five fifty-three, execute a missed approach, make a left turn to a heading of --- one eight zero, climb to two thousand [between words 'of' and 'one' there is a pause and a voice in the background says 'one eighty'] |
| 20.27:05.74 | CAM | [Sound of stickshaker begins and continues to end of recording] |
| 20.27:07.56 | CAM-? | [Two to three hurried word at very low amplitude and masked by noise of stickshaker] |
| CAM | [Sound of click - similar to sound made by flap lever moving into detent] | |
| 20.27:12.14 | RDO-2 | Okay, left turn to one eight zero, --- left turn okay? |
| 20.27:13.88 | CAM-3 | Want more flaps? |
| 20.27:15.33 | CAM-? | Flaps fifteen. |
| 20.27:15.45 | MTWR | Yeah, make left turn to one eighty. |
| 20.27:16.14 | CAM-? | I'm sorry. |
| 20.27:16.47 | CAM | [Sound of click - similar to sound made by flap lever moving into detent] |
| 20.27:19.4 | CAM | [Sound of click - similar to sound made by landing gear lever moved out of detent] |
| 20.27:20.14 | CAM | [Sound of double click - similar to sound made by landing gear lever moved into up detent] |
| 20.27:10.64 | CAM | [Sound of landing gear warning horn begins and continues to end of recording] |
| 20.27:23.55 | CAM | [Sound of initial impact and garbled voice] |
| 20.27:24.46 | RDO-1 | [Sounds of impact and unintelligible voice] |
| 20.27:25.02 | RDO-1 | end of recording. |