Boeing 747SP-21 accident near Midway Islands, PO, December 23, 1988
On December 23, 1988 at about 10:30 am local time, a Boeing 747SP-21, registered N146UA, was involved in an accident near Midway Islands, PO. It was a flight of an unrecorded kind under scheduled airline rules (Part 121). 1 person was seriously injured and 1 person had minor injuries; 220 others were unhurt. The weather was conditions the NTSB did not record.
The NTSB's probable cause their words, unchanged
AIRCRAFT'S ENCOUNTER WITH UNFORECAST SEVERVE CLEAR TURBULENCE.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- December 23, 1988 · about 10:30 am local time
- Place
- Midway Islands, PO · map
- Type
- Accident
- Injuries
- 1 person was seriously injured and 1 person had minor injuries; 220 others were unhurt.
- Weather
- conditions the NTSB did not record
- Aircraft
- Boeing 747SP-21 · all 747SP-21s on the register
- Registration
- N146UA · registry record · serial 21547
- Damage
- Not recorded
- Flight
- Flight of an unrecorded kind · scheduled airline rules (Part 121)
The NTSB's narrative final · quoted from the NTSB record
UNITED AIRLINES FLT 820 WAS ENRTE FROM NORITA, JAPAN TO SAN FRANCISCO, CA. AT FLT LVL 380 SEVERE CLEAR AIR TURBULENCE WAS ENCOUNTERED. THREE CABIN CREW MEMBERS WERE THROWN TO THE CEILING, TWO OF WHOM WERE INJURED, ONE SUSTAINING A FRACTURED LEG. THE FLT DIVERTED TO HONOLULU AND LANDED WITHOUT INCIDENT. BOTH FLT AND CABIN CREW REPORTED THAT THERE HAD BEEN NO WARNING OF ANY IMPENDING TURBULENCE PRIOR TO ABRUPTLY ENCOUNTERING THE TURBULENCE THAT CAUSED THE INJURIES, AND THAT THE SEAT BELT SIGN WAS TURNED OFF.
The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.
The factual record from the NTSB's investigation tables, in plain English
Pilot
- Certificate: airline transport pilot
- Ratings: multi-engine land; single-engine land; instrument: airplane
- Flight time: 22,735 hours in all; 810 in this make and model; 40 in the last 90 days
- Medical certificate: Class 1 (valid medical--no waivers/lim.)
- Seat: left
The aircraft
- Last inspection: approved inspection programme
- Maximum gross weight: 360,000 lb
- Seats: 331
- Landing gear: retractable
- Engine: P&W JT-9D (turbofan); 0 hours total
- Operator: United Airlines
The flight
- Departed from: NRT Norita OF
- Destination: SFO San Francisco CA
- Flight plan: IFR
- Runway 0
- A second pilot was aboard
Weather at the time
- Light: dawn
- Visibility: 50 statute miles
- Sky: clear
- Temperature: 50°F (10°C), dew point 0°F (-18°C)
- Altimeter: 29.00 inHg
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 1 | 1 | 12 | |
| Passengers | 208 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
The docket, the folder of records gathered during an investigation (maintenance records, photographs, witness statements, examinations), has not been read from the NTSB for this case yet; the list appears here once it has. Open the docket at the NTSB.
Everything on this page comes from the NTSB's public records. The narrative, probable cause and findings are the NTSB's own words; the coded tables behind the report are written out in plain English, with pilots' ages, home towns and medical details left out. The documents and photographs are the NTSB's docket, shown as the NTSB released them. This site's own text never names anyone involved. A preliminary report can change; the final report usually follows one to two years later, and the page is refreshed when it does.