A knot is a unit of speed that is used to measure how fast airplanes are traveling. It is equal to one nautical mile per hour, which almost 1,000 feet further than a regular mile-per-hour.
The plane that crashed, which was operated by Asiana Airlines, was coming into San Francisco after a flight from Seoul, South Korea. The plane was carrying 307 people, and two were killed in the accident.
More than 180 passengers were hospitalized after the crash, which was the first major commercial airline crash in the U.S. since a 2009 regional plane accident in Buffalo, N.Y.
Hersman said on Monday that the pilots of the Asiana Airlines flight might have realized they were approaching the San Francisco airport incorrectly.
“1.5 seconds before impact, they … call for a go-around,” she said. “This is communication between the two pilots, basically saying they want to abort the landing and go around and try again. This is very helpful to our investigators as far as focusing our investigation.”
Hersman expressed confidence that more information about the crash would become available to the public soon.
“We have 24 hours of flight data recorder information; we have two hours of [cockpit voice recordings]; we’ve got good radar returns, and we’re going to put all of that together,” the NTSB chief said. “We will release more factual information in the coming days.”