Germany's busiest airport was forced to cancel more than 100 flights on Thursday morning after climate activists breached security and blocked runways by gluing themselves to the tarmac.
Officials took to social media platform X to advise passengers not to travel to the airport and to check their flight status, warning of potential delays.
The protest was orchestrated by the Last Generation climate group, which claimed that six of its members had cut through a fence to access various points around the runways.
Activists were seen holding posters with the message "Oil kills". Images released by the group showed protesters wearing orange high-visibility vests with their hands affixed to the tarmac.
A police spokesperson confirmed the presence of several climate activists on airport grounds.
The airport said shortly before 8am that flight operations were “gradually resuming”, and it later said that all runways were back in operation.
It added that about 140 flights had been cancelled so far - roughly a tenth of the flights scheduled for Thursday.
The action is part of a broader campaign by Last Generation, which began on Wednesday and is set to include similar disruptions across Europe and North America.
The group reiterated its demand for the German government to participate in shaping and signing a global agreement to phase out oil, gas, and coal by 2030.
It follows similar incidents at Heathrow and Germany's Cologne-Bonn airport, the country's sixth-largest, where flights were suspended for several hours on Wednesday after activists glued themselves to a runway.
On Wednesday, Just Stop Oil (JSO) members cycled round the perimeter of Heathrow before being taken into custody on suspicion of conspiring to interfere with a site of key national infrastructure under the Public Order Act.
JSO hailed the start of “the international uprising” as it posted a video of the arrested activists. Sean Callaghan, 29, was filmed saying: “I'm taking action with Just Stop Oil at airports this summer because it is impossible for me to see a way in which we can inspire and enthuse students about the future of our planet.”
A Heathrow spokesman said: “We are in full agreement that the aviation industry needs to decarbonise, but unlawful and irresponsible protest activity will not be tolerated.”
Last Generation activist Ronja Kuenkler said that Wednesday's protest was "just the beginning" but declined to comment on whether the Paris Olympics, due to start on Friday, would be targeted by the group.
