British fighter aircraft escorted a plane from Cairo bound for New York to an emergency landing in the U.K. after a passenger discovered a letter onboard threatening to blow up the aircraft, officials said Saturday.

Flight 985 to John F. Kennedy Airport had around 300 passengers onboard when it was diverted to Glasgow’s Prestwick Airport after a passenger found the letter in a lavatory, EgyptAir chairman Tawfiq Assi said.

Britain’s Ministry of Defense confirmed that that fighter jets were scrambled to escort the plane to the Glasgow airport, but referred further questions to police in Glasgow.

Police in Glasgow confirmed that officers were responding to an incident but declined to provide further detail.

Assi said the flight is now being checked by a technical team that includes bomb disposal experts.

Passengers were let off to wait in Glasgow’s airport, and officials are also looking into their backgrounds, he said, adding that the flight hopefully will resume its journey to New York following inspections.

Read more: NY Daily News