Climate protesters disrupted flights all across Europe on Thursday after they breached security fences at Frankfurt Airport, Germany’s busiest hub for international travel. Airport security joined police and firefighters in removing the protesters, but not before at least 140 flights were canceled, with more cancellations expected to follow.

“We sharply condemn these unauthorized demonstrations, and we reserve the right to take legal action against the participants,” Frankfurt Airport said in a statement. “Their activities pose severe danger to flight operations — possibly putting human life at risk.”

A climate group known as Last Generation organized the demonstration, the second in as many days to disrupt a German airport. Five protesters glued themselves to a taxiway at Cologne-Bonn Airport on Wednesday, forcing a roughly three-hour delay in flights. Climate activists staged similar demonstrations at other locations throughout Europe, including in Finland, Norway, Switzerland and Spain. Last Generation and its supporters are calling on governments to ban the extraction and burning of all fossil fuels by 2030 — at this point, a virtually impossible goal.

The Last Generation protests come on the heels of record-breaking temperatures fueled by climate change. In the 2023, Earth set a new global surface temperature record, a new record for the hottest summer temperature and a new record for ocean heat content. Overall 2023 was the warmest year ever recorded since humans began keeping temperature records, and the early months of 2024 have followed suit. Indeed, the planet experienced its two hottest days ever recorded, last Sunday and Monday.

In a statement to the Associated Press, Christiana Figueres, the former head of U.N. climate negotiations, warned that humanity will “scorch and fry” if government and business leaders do not implement “targeted national policies” to sharply reduce fossil fuel extraction and emissions.