Casualties unknown

Turbulence Encounter at Flight Level 350 (N645UA)

Caribbean Sea, US

On July 16, 1993, a Boeing 767-322ER (registration N645UA) operated by United Air Lines, Inc. was involved in an aviation accident near Caribbean Sea. Investigators recorded the probable cause as: TURBULENCE ENCOUNTERED DURING CRUISE FLIGHT AFTER ENTERING CIRRUS CLOUDS. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.

Sourcesthe U.S. National Transportation Safety Board (NTSB) historical archivePrimary reportUpdated 2026-06-19Data APIEditorial standards
Aircraft registered N645UA
Aircraft registered N645UA. Photo: Aero Icarus from Zürich, Switzerland / CC BY-SA 2.0, via Wikimedia Commons

A flight experienced two sharp jolts of turbulence while cruising at flight level 350, encountering cirrus cloud tops despite clear weather radar returns.

What happened

The aircraft was operating in cruise flight conditions when it reached flight level 350. At this altitude, the flight path intersected the tops of cirrus clouds. Shortly after entering this region, the occupants experienced two distinct and sharp jolts of turbulence. These disturbances lasted for approximately 15 seconds before subsiding.

At the time of the incident, the onboard weather radar was active. The display showed no precipitation or weather returns, indicating that the aircraft was not flying through any detectable storm cells or convective activity based on radar data.

The flight continued without further interruption to its scheduled destination. Upon arrival, the injured flight attendants were removed from the aircraft and received medical treatment.

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Frequently asked questions

What happened in the 16 Jul 1993 Boeing 767-322ER accident near Caribbean Sea?

A flight experienced two sharp jolts of turbulence while cruising at flight level 350, encountering cirrus cloud tops despite clear weather radar returns.

What aircraft was involved and where did it happen?

The accident on 16 Jul 1993 involved a Boeing 767-322ER, registration N645UA, operated by United Air Lines, Inc., at Caribbean Sea.

What was the probable cause of the accident?

TURBULENCE ENCOUNTERED DURING CRUISE FLIGHT AFTER ENTERING CIRRUS CLOUDS.

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001211X12985. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.