A man and his companion were escorted off a flight when he received a text saying he had tested positive for coronavirus.
The passengers had just boarded the Ryanair service to Pisa, Italy, from Stansted Airport when the message came through.
After alerting cabin crew, the man and his travel partner were taken to an isolation area at the terminal.
Ryanair said both passengers were seated for only 10 minutes.
The flight on Wednesday was delayed by one hour and 20 minutes while seats and overhead cabins were disinfected.
A video of the passengers being removed by officials in protective suits has been posted on social media.
Ryanair said the pair had complied fully with the airline’s health regulations and had both worn masks at all times at Stansted Airport.
The company said there “was little if any risk of Covid-19 transmission to other passengers or crew members”.
A Stansted Airport spokesman said members of its fire service attended the aircraft and escorted the passenger and travel partner to an isolation area.
Once there, they were put in contact with Public Health England “who then oversaw the passenger’s onward journey”, he said.