On January 4, 2024, Alaska Air Flight 322 experienced a runway excursion after landing at Boston Logan International Airport during a winter storm. The Boeing 737-900ER carrying 152 passengers and crew slid off the paved surface into snow, resulting in no major injuries but triggering intense scrutiny from federal safety investigators.
Understanding this incident requires looking past basic news summaries to examine precise meteorological data, aircraft telemetry, and operational decisions made during winter weather events. Let's break down the sequence of events, root causes, and safety lessons stemming from the event.
Flight Route and Aircraft Profile
The journey began at Las Vegas Harry Reid International Airport before making a scheduled stop in Seattle. The final leg from Seattle-Tacoma International Airport to Boston Logan put the aircraft squarely in the path of developing East Coast winter squalls.
- Aircraft Type: Boeing 737-900ER
- Registration: N331AK
- Flight Segments: LAS to SEA, then SEA to BOS
- Passenger Load: 152 occupants (passengers and crew)
The transcontinental flight was roughly 45 minutes behind schedule upon entering the Boston terminal airspace due to congestion and earlier weather delays along the route. Despite the schedule pressure, the flight crew maintained a stable approach profile until the final descent phase.
Weather Dynamics at Boston Logan
Meteorological conditions at Boston Logan around 9:30 p.m. local time created severe operating hurdles. Ground sensors recorded a temperature hovering right at the freezing point of 32 degrees Fahrenheit, accompanied by strong south-southeast winds gusting up to 29 knots.
Visibility had dropped to three-quarters of a mile due to moderate snow falling at a rate of 2 to 3 miles per hour. This low-ceiling and low-visibility environment forced the flight crew to rely heavily on instrument guidance until acquiring visual references near the runway threshold.
The Landing Sequence and Excursion Breakdown
The cockpit voice recorder and flight data recorder later revealed a standard ILS approach until touchdown on Runway 15R. Witnesses and telemetry data highlighted the following sequence of events:
- Initial Touchdown: The aircraft touched down near the runway centerline at approximately 8:42 p.m. local time.
- Braking Application: Pilots immediately engaged wheel brakes and thrust reversers, but deceleration was severely compromised by surface contaminants.
- Loss of Control: The aircraft began drifting to the right due to a combination of crosswinds and reduced tire traction on slush.
- The Excursion: Both main landing gear departed the paved surface, sending the jet sliding roughly 950 feet across a snow-covered safety area before coming to a stop near the airport perimeter.
- Emergency Evacuation: The captain ordered an emergency evacuation via slides, and airport rescue teams transported all occupants to the terminal via bus.
NTSB Findings and Surface Friction Analysis
The National Transportation Safety Board launched an immediate investigation into the mishap. Investigators discovered that while the top layer of Runway 15R appeared cleared or lightly snow-covered, a hidden layer of compacted snow and wet slush lay underneath.
This condition drastically reduced the tire-to-ground friction coefficient. Even with maximum braking inputs, the aircraft lacked the necessary grip to stay aligned with the runway centerline. The NTSB report emphasized that environmental factors and runway contamination levels overwhelmed the braking margins, compounding the challenge for the flight crew.
Industry Adjustments and Winter Operations
The incident served as a wake-up call for major carriers operating in northern climates during winter months. Airlines updated their internal decision-making policies to adopt more conservative diversion thresholds when runway braking action reports show significant deterioration.
Furthermore, airports have refined their real-time friction measuring protocols to give pilots more accurate data before touchdown, reducing the risk of unexpected hydroplaning on slush-covered tarmac.
Frequently Asked Questions
Were there any injuries during the Alaska Air Flight 322 excursion?
No serious injuries were reported among the 152 passengers and crew members on board. Minor bumps and scrapes occurred during the emergency evacuation slides, but all occupants were evaluated and cleared by medical personnel at the terminal.
What caused the aircraft to slide off the runway?
Investigators determined that reduced runway friction caused by a hidden layer of wet slush and compacted snow beneath fresh snow prevented the tires from maintaining traction during maximum braking.
Which runway was involved in the incident?
The aircraft landed on Runway 15R at Boston Logan International Airport (Massport) before sliding onto the adjacent safety area.
What aircraft model operated Flight 322?
The flight was operated using a Boeing 737-900ER twin-engine narrow-body jet owned and operated by Alaska Airlines.
