A Ryanair flight declared a mid-air emergency after its co-pilot fell ill just 13 minutes after take-off.
The plane was full of holidaymakers leaving Tenerife for Scotland when the drama unfolded.
The flight was forced to do a U-turn and return back to the island's south airport where the emergency services were activated.
The budget airline has confirmed the incident but was unable to give further information about the co-pilot's condition due to privacy laws.
The alert happened on Sunday on the Prestwick flight just 13 minutes after it had departed from Tenerife.
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Air traffic controllers tweeted: "Flight from Tenerife South to Scotland returns in emergency due to medical problem of one of the pilots. Maximum priority.
"The route is cleared, medical attention is coordinated and the emergency protocol is activated."
The plane landed normally and did not have to burn fuel, as is usually done when there is a technical problem to reduce the weight of the aircraft and facilitate the approach operation.
Airport sources said pilots are fully trained to deal with such incidents and one of them can fly the aircraft alone.
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A spokesperson for Ryanair said: "This flight from Tenerife to Glasgow (April 7th) returned to Tenerife Airport shortly after take-off after the first officer became ill inflight.
"In line with procedures, the captain contacted ATC, the aircraft landed normally, and the first officer was met by medical personnel.
"Customers disembarked and departed to Glasgow shortly afterwards.”
