Alaska Airlines Flight 684
Boeing 737-242C · Accident: in flight encounter with weather en route
From Seattle–Tacoma International Airport (SEA) to Harry Reid International Airport (LAS)
Event
- NTSB case
- LAX98LA104
- Event typeAccident: someone killed or seriously injured, or the aircraft substantially damaged (NTSB definition). Incident: an occurrence that affected or could have affected safety, short of that. Glossary
- Accident
- InvestigationHow far the investigation had got when the record was published: preliminary, ongoing, final or completed. Unknown where the source does not say. Glossary
- Completed
- API-reported fatalities
- 0 · all aircraft and ground
- Ground fatalities
- 0
- OperationWhat kind of flying it was, grouped by the rules it flew under: airline (US Part 121), air taxi and commuter (Part 135), general aviation (Part 91 and similar), military or government. Glossary
- Airline
- WeatherVisual meteorological conditions (VMC): good enough to fly by looking outside. Instrument conditions (IMC): cloud or low visibility, flying by instruments. Glossary
- Visual Meteorological Cond
Boeing 737-242C
- Aircraft type
- Boeing 737
- Category
- Airplane
- RegistrationThe aircraft's tail number, such as N12345 or G-ABCD. Registrations are reissued, so the same one years apart can be a different aircraft. Glossary
- N746AS
- Operator
- Alaska Airlines
- Onboard fatalities
- Unknown
- Route
- From Seattle–Tacoma International Airport (SEA), Seattle, WATo Harry Reid International Airport (LAS), Las Vegas, NV
- Aircraft age
- Not recorded
- Flight rulesThe regulations the flight operated under: in the US, Part 91 (general aviation), Part 121 (airlines), Part 135 (air taxi and commuter) and others; for flights abroad, the NTSB's coarser commercial or non-commercial code. Glossary
- Part 121: Air Carrier
- Phase of flightThe stage of the flight when things started to go wrong: standing, taxi, takeoff, initial climb, en route, maneuvering, approach or landing. Glossary
- En route · cruise
- First occurrenceThe single coded event the NTSB judges best describes what happened (records from 2008 on). Older records name the first occurrence in the sequence instead. Glossary
- In flight encounter with weather
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- None
Cause areas
- Weather condition › Turbulence, clear air
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
The fight encountered severe clear air turbulence en route at flight level 350 and diverted to Reno, Nevada.. There were no reports of clear air turbulence from other pilots nor was it forecasted. The seat belt signs were off at the time. A review of the flight data recorder indicated that, for the period involved, vertical acceleration (Nz) varied from +1g to +1.5g to -0.07g to +1.3g to +0.86g over a 6-second period. The recorded data also indicated that atmospheric stability existed at flight level 350 several minutes prior to the turbulent onset. There was little or no warning given to the flight crew of the impending turbulent conditions.
Probable cause
Unforecasted and sudden encounter with clear air turbulence when passengers and flight attendants were not secured in their seats.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record LAX98LA104
- Event ID
- 20001211X09708
- Case number
- LAX98LA104
- Dataset
- historical-pre2008
- Source SHA-256
- 89e2df6d848e7ab3b42e7d7c7a03ff403303057a26ca04c95b3ea67201c3ce74
Source notes (5)
- Unreviewed is an editorial label, not an investigation status. API-sourced is not report-checked or human-reviewed. Explicit event totals are used without summing aircraft injury tables; onboard allocation is withheld. Unknown values remain unknown. The operation category is mapped from the NTSB-reported FAR part and has not been reviewed.
- Filled from the NTSB case API where the bulk record had no value: investigation status, damage. Values present in the bulk record are kept.
- The date is the local date, which is the same as the UTC date the NTSB stores.
- API snapshot SHA-256: 10fb11f6735326b76d177f5516ce0d2791ed8aa88126a201e3d6be339eeab019; retrieved 2026-09-18T17:12:20.547Z.
- The NTSB's operator name is blank for N746AS; the operator shown is the name the NTSB's other records give its FAA operator code, ASAA.