Gulfstream G-II accident near Cheyenne, Wyoming, July 28, 1990
On July 28, 1990, a Gulfstream G-II, registered N405MM, was involved in an accident near Cheyenne, Wyoming. It was an executive or corporate flight under general aviation rules (Part 91). 1 person was seriously injured and 7 people had minor injuries; 2 others were unhurt. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
AN UNFORESEEN ENCOUNTER WITH CLEAR AIR TURBULENCE.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- July 28, 1990
- Place
- Cheyenne, Wyoming · map
- Type
- Accident
- Injuries
- 1 person was seriously injured and 7 people had minor injuries; 2 others were unhurt.
- Weather
- visual conditions (good weather)
- Aircraft
- Gulfstream G-II
- Registration
- N405MM · registry record · serial 220
- Damage
- Not recorded
- Flight
- Executive or corporate flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
THE AIRPLANE WAS APPROXIMATELY 100 NM NORTHEAST OF DENVER, DEVIATING AROUND THUNDERSTROM ACTIVITY, WHEN CLEAR AIR TURBULENCE (CAT) WAS ENCOUNTERED. THE CAPTAIN STATED AFTER THE ACCIDENT THE FLIGHT ATTENDANT HAD LEFT HIS SEAT TO PERFORM CABIN DUTIES AND WAS SQUATTING DOWN IN THE GALLEY WHEN THE AIRPLANE WAS BUFFETED BY THE TURBULENCE. TH FLIGHT ATTENDANT INJURED HIS ANKLE WHILE IN THIS POSITION. THE AIRPLANE RETURNED TO ENGLEWOOD, CO., AND THE FLIGHT ATTENDANT WAS TRANSPORTED TO THE HOSPITAL. ACCORDING TO THE DENVER ARTCC, THERE WERE NO REPORTS OF TURBULENCE BY OTHER AIRCRAFT PRIOR TO THE ENCOUNTER.
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
- Ratings: multi-engine land; single-engine land; single-engine sea; instrument: airplane
- Medical certificate: Unknown
- Seat: unk
The aircraft
- Last inspection: inspection type not recorded; 0 hours since
- Maximum gross weight: 64,800 lb
- Seats: 15
- Landing gear: retractable
- Engine: Rolls-Royce SPEY MK 511-8 (turbofan); 0 hours total
- Operator: Martin Marietta Corporation
The flight
- Departed from: APA Englewood CO at 11:00 pm
- Destination: IAD Centerville VA
- Flight plan: IFR
- Runway 0
Weather at the time
- Light: daylight
- Wind: from 210° at 12 knots, gusting 16
- Visibility: 50 statute miles
- Sky: broken clouds at 16,000 ft; scat at 7,500 ft
- Temperature: 81°F (27°C), dew point 45°F (7°C)
- Altimeter: 30.00 inHg
- Observation at 11:50 pm from DEN, 75 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 1 | 2 | ||
| Passengers | 7 |
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.