“The pilots were talking about getting down to a safe altitude.
Well it was stupid of the pilots to announce it the way they did.”
His first thought was to control the plane and keep everyone safe, not the proper wording for the warning to the passengers. If he had more time, he might have said it differently, But if I were a passenger, I’d be happy that he focused on the job, and not the proper way to word the emergency.
My impression is the pilot usually says nothing until the desired altitude is reached. Rapid descent can involve some serious maneuvers.
Here's a chart of the flight in question.
http://flightaware.com/live/flight/SWA3426/history/20131112/2130Z/KTPA/KRDU/tracklog
He was flying at 41,000 feet. That's the maximum service ceiling for the 737-700, and quite high for a 75 minute flight.
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