The Delta Air Lines Boeing 767-300 plane sounded the alarm while traveling near Argyll and Bute Council in Scotland. The 7700 code indicates a “general emergency” and usually means a technical problem with the aircraft.
It is not yet known why the 7700 signal was broadcast.
The destination is unknown.
Writing for Flightradar24, Ken Hoke, a Boeing flight captain, explained that “screeching” is one way an aircraft reports an emergency to air traffic control so they can get help on the ground.
He said it could be an “aircraft problem or medical problem”.
Mr Hoke said: “If a crew resets their transponder to emergency code 7700 (squawking 7700), all air traffic control facilities in the area are immediately notified that the aircraft is in an emergency.
“It is up to the crew to let ATC know what the exact situation is. It could be an aircraft problem, a medical problem or something else.
“In some cases, a crew cannot choose to change their transponder to 7700 (it is not required). If I talk to Chicago Approach and have a problem, I will tell them the problem, report an emergency over the radio and land vectors immediately.”
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