NTSB CAROL · Event
Event WPR12LA053
Registry · N261WN
FAA Aircraft Registry record.
Make / Model
BOEING 737-7H4
Year of manufacture
2006 · 5 years old at event
TCDS
A16WE · THE BOEING CO
Engine
CFM INTL CFM56-7B24
Seats / Engines
143 seats · 2 engines
Last airworthiness date
20061213
ADS-B equipped
Yes — Mode-S A284B5
Registrant of record
SOUTHWEST AIRLINES CO
Source: FAA Aircraft Registry (releasable master file).
Aircraft involved
Probable cause & findings
The flight crew’s flight into known severe turbulence associated with mountain wave activity.
Factual narrative
HISTORY OF FLIGHT
On December 1, 2011, at 1953 Pacific standard time, a Boeing 737-7H4, N261WN, flight 1489, encountered turbulence at flight level 30,000 feet (FL300), over Yosemite National Park, California. One flight attendant sustained serious injuries; 2 flight attendants received minor injuries; 2 pilots and 95 passengers were not injured. Southwest Airlines operated the flight under the provisions of 14 Code of Federal Regulations Part 121, as a scheduled-passenger flight that departed Albuquerque International Sunport Airport (ABQ), Albuquerque, New Mexico. An instrument flight rules (IFR) flight plan had been filed. The flight was destined for Metropolitan Oakland International Airport (OAK), Oakland, California. According to Southwest Airlines, the airplane had been at FL400 and was descending to FL300 when the flight encountered severe turbulence. All three flight attendants were not seated when the turbulence was encountered. One flight attendant was in the forward galley and the other two flight attendants were in the aft galley. When the turbulence was encountered, the flight attendant in the forward galley was thrown up and down, and side to side with her feet leaving the cabin floor. She was able to hold onto a counter, and was eventually able to secure herself in the forward jumpseat. The two flight attendants in the aft galley were thrown around the aft galley and struck their heads and backs; they also were eventually able to secure themselves in their respective jumpseats and remained there throughout the landing. Both flight attendants were transported to the hospital via ambulance. One flight attendant was released with minor injuries. The other flight attendant was released from the hospital as well, and was informed the following day of the compression fracture of his vertebrae. There were no passengers transported to the hospital. According to statements from the flight attendants, they had been advised by the flight crew to secure the cabin early because the flight crew was expecting turbulence later in the descent. Statements from the flight crew indicated that the flight attendants had to be seated multiple times throughout the flight due to turbulence. The captain reported that they had descended from FL400 to FL300 due to moderate turbulence. They were authorized to stop at any smooth altitude. The crew had continuous turbulence through FL320. At FL300, the ride was better, but shortly thereafter, they encountered abrupt and significant severe turbulence for approximately 10 seconds. The aircraft accelerated from .760 mach to .865 mach with vertical pitch change and associated yaw. They requested an immediate descent and checked on the status of the cabin crew and passengers. They were then advised of the injuries to the cabin crew. They declared an emergency and landed at Oakland where they were met by medical personnel. In a statement submitted by the first officer, he reported that upon departure, they requested that the flight attendants remain seated until called. About 45 minutes after departure, the captain cleared the flight attendants to move around the cabin. The flight encountered additional turbulence, and the captain requested that the flight attendants take their seats. As the flight continued, it encountered intermittent moderate turbulence at FL400 and they requested a different altitude. The flight descended to FL300. All passengers were in their seats because the seatbelt sign was on, but the three flight attendants were not seated. The first officer could not recall the captain clearing the flight attendants from their seats. According to statements submitted by the flight attendants, the flight crew informed the flight attendants that they were going to have them secure the cabin 35 minutes early due to projected turbulence. Shortly thereafter, the flight encountered severe turbulence. During the encounter, all flight attendants were lifted from the floor from the turbulence and unsecured service items were strewn about the galleys. According to a statement from the dispatcher, the flight had been planned and filed to descend to FL260 prior to entering the area where the event occurred.
FLIGHT RECORDERS
The cockpit voice recorder (CVR) was examined. The recording consisted of four channels of audio information; however, none of the audio was pertinent to the incident/accident investigation. The audio was consistent with the CVR being overwritten or recorded over by subsequent events. Data obtained from the flight data recorder (FDR) showed at 1931, the airplane was in level flight at 40,000 feet, and was experiencing vertical accelerations of about +/- 0.1g. At 1943:05, the aircraft descended to 30,000 feet. The flight management computer (FMC) computed wind speed showed a significant increase in wind speed at 30,000 feet compared to 40,000 feet. At 1953:21, when the airplane was level at 30,000 feet, it began experiencing vertical accelerations for about 13 seconds. During this period, the maximum negative and positive vertical accelerations were -0.18g and +3.52g, respectively.
METEOROLOGICAL INFORMATION
A Senior Meteorologist reviewed weather information pertinent to the flight. Synoptic conditions were favorable for mountain wave activity over California, and the National Weather Service had issued significant meteorological information (SIGMET) and airman’s meteorological information (AIRMET) notices for turbulence over the region. Additional information was included in the flight crew’s weather document from their enhanced weather information systems (EWINS) provider (SW45), which expected severe turbulence between FL300-420. The event occurred in the region that the SIGMET and SW45 had been issued. No visual sign of the turbulence other than some lower cap or lenticular clouds over the peaks were noted, but visual meteorological conditions (VMC) prevailed at their location. The flight was transitioning through an area of known severe turbulence. One of the flight attendants reported that the flight crew asked the cabin crew to secure the cabin early as they expected to encounter turbulence during the descent. Shortly thereafter, the airplane encountered severe turbulence and the flight attendants were thrown about the galley; one sustained a serious injury. The cockpit voice recorder contained audio that was not relevant to the flight (it was likely recorded over by subsequent events), thus it could not be conclusively determined when the flight crew asked the flight attendants to be seated because they could not recall. It is likely that the flight crew’s request for the cabin to be secured was close to the time of the turbulence encounter, since none of the flight attendants had completed securing the service items when the encounter occurred. Synoptic conditions were favorable for mountain wave activity and a significant meteorological information (SIGMET) advisory and airmen’s meteorological information advisories had been issued for turbulence over the region. The flight crew also had an advisory issued from their enhanced weather information systems for severe turbulence. The event occurred in the region that the SIGMET and the advisory for severe turbulence had been issued. According to the filed flight plan, the flight was to descend before entering the advisory area for weather avoidance; however, the planned descent was not followed. Source: NTSB Aviation Accident Database Retrieved: 2026-02-12
NTSB Findings
Hierarchical cause / factor breakdown from the FAA bulk avdata database. Each finding tagged C (Cause) or F (Factor).
- C Environmental issues-Conditions/weather/phenomena-Turbulence-Clear air turbulence-Effect on personnel - C
- C Personnel issues-Action/decision-Action-(general)-Pilot - C
Verbatim from NTSB's published report. Source file
NTSB_2011_WPR12LA053.txt.
Findings + structured fields enriched from FAA avall.mdb.
Full investigation docket on
data.ntsb.gov ↗.
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Related research
What the literature says.
Academic papers and agency reports matching this event's aircraft type or causal vocabulary (turbulence). Sourced from NASA NTRS, NTSB Safety Studies, FAA CAMI, AOPA Air Safety Institute, Embry-Riddle Scholarly Commons, arXiv, and the Semantic Scholar academic graph.
- arXiv 2026 · arXiv preprint
Direct Numerical Simulations of Ice-Ocean Boundary Turbulence
Turbulent heat and freshwater transport at ice-ocean interfaces controls glacier and iceberg melt rates, yet the underlying physics remains poorly constrained.
- Embry-Riddle Scholarly Commons 2025 · Journal article (JAAER)
Political Turbulence and Aviation Safety: A Cross-National Analysis of Political Stability's Effects on Aviation Accidents
To what extent does political stability affect aviation safety? This research aims to link domestic political conditions and public safety through the consideration of aviation accident frequency.
- arXiv 2025 · arXiv preprint
Explainable LiDAR 3D Point Cloud Segmentation and Clustering for Detecting Airplane-Generated Wind Turbulence
Wake vortices - strong, coherent air turbulences created by aircraft - pose a significant risk to aviation safety and therefore require accurate and reliable detection methods.
- arXiv 2024 · arXiv preprint
Does small-scale turbulence matter for ice growth in mixed-phase clouds?
Representing the glaciation of mixed-phase clouds in terms of the Wegener-Bergeron-Findeisen process is a challenge for many weather and climate models, which tend to overestimate this process because…
- arXiv 2023 · arXiv preprint
Effects of electrostatic interaction on clustering and collision of bidispersed inertial particles in homogeneous and isotropic turbulence
In sandstorms and thunderclouds, turbulence-induced collisions between solid particles and ice crystals lead to inevitable triboelectrification.
- SKYbrary (Eurocontrol) 2023 · SKYbrary article
Wake Vortex Turbulence — SKYbrary Knowledge Base
SKYbrary wake vortex turbulence comprehensive article — generation mechanics, dissipation factors, separation standards (ICAO LIGHT/MEDIUM/HEAVY/SUPER + recategorisation RECAT-EU).
Browse the full corpus — academia portal ↗