About 40 activists from Extinction Rebellion blocked the private jet terminal at Brussels Airport on Monday morning, Belga News Agency reports.

The activists plastered messages on the terminal’s windows and chained themselves to the entrance. Their action is part of the international “Make them pay” campaign, which aims to enforce substantial taxes on the most frequent users of air travel and to ban private flights.

The police, present in large numbers, do not appear to have any immediate intention of intervening to remove the activists.