The passenger, who has not been identified, and his travel companion were on a flight to Pisa, Italy, from London Stansted airport on Wednesday when he received the text message before departure.
Ryanair said in a statement that they were both seated for only 10 minutes before they were taken off the plane and taken to an isolation area at the airport.
The flight to Pisa went ahead after a delay of one hour and 20 minutes while seats and overhead cabins were disinfected.
Ryanair said in its statement: “Since this passenger and his companion had complied fully with Ryanair health regulations, they were both wearing masks at all times at Stansted Airport and for the very short period – less than 10 mins – they were seated on the aircraft prior to departure.
“There was little if any risk of Covid-19 transmission to other passengers or crew members as all of whom were also wearing face masks at all times.
“The aircraft departed for Pisa following a delay of one hour and 20 mins to allow for the empty seats and overhead cabin bins to be disinfected to comply with all UK health authority guidance.
“Ryanair apologises to all passengers for this short delay.”
A spokesman from Stansted Airport said: “We were made aware of the passenger by the airline and members of the airport’s fire service attended the aircraft and escorted the passenger and travel partner to an isolation area, where they were put in contact with Public Health England who then oversaw the passenger’s onward journey.”
