Lufthansa expects actions by climate activists on the flights themselves, according to an internal document published by German media on Sunday.

"Activists, as regular passengers, could enter the plane and disrupt the flight, or even stop it," said an internal warning sent to employees by Lufthansa management, Hina reported.

Aircraft can also be "polluted" with paint, as was already the case with works of art or cultural monuments such as the Brandenburg Gate. When asked by the media, Lufthansa declined to provide details, citing sensitive security issues. For the past few days, in the midst of the holiday season, climate activists have stormed airports and blocked traffic by clinging to the runways. On Friday, police in Hamburg arrested several activists who were trying to enter the airport and block traffic by clinging to the runways.

Lawyers told German media that deliberately disrupting a flight on the plane itself could have serious legal consequences for activists, including years in prison. Members of the "Last Generation" movement have announced that they will continue their protests until the German government takes "sufficient steps" that would lead to Germany ending its use of fossil fuels by 2030.