Frankfurt airport, Germany's busiest, was forced Thursday to temporarily suspend arrivals and departures after environmental activists forced their way into the apron.
Traffic was halted during the busy summer holiday season for two hours before the first of the airport's landing runways was able to operate again at 05:02 GMT, said a spokesman at the airport.
A departures runway reopened shortly afterwards, said the spokesman, with a second to follow imminently.
Passengers were advised to check the status of their flights while the airport ramps up its operations again.
Police had said earlier that they "doing everything" to get the protesters off the tarmac.
According to climate activist group Letzte Generation (Last Generation), six of its members had used pincers to cut openings in the wire fence before making their way "by foot, with bicycles and skateboards to different points around the runways".
A photo circulated by the group depicted a protester sitting on the tarmac with an orange banner "oil kills".
The group is pushing for a binding international accord that would lead to an end in oil, gas and coal use by 2030.
Concerted protest action
Thursday's protest action came a day after similar operations across several European airports.
Activists from Letzte Generation disrupted traffic at Cologne-Bonn airport for several hours on Wednesday by glueing themselves on the tarmac.
Several climate protesters were arrested at London's Heathrow airport.
The protest organisers are part of the A22 Network of groups committed to non-violent climate protests, which said it was planning to disrupt airports in several countries in the coming months.
Protests were planned in Britain, Austria, the Netherlands, Switzerland, Canada, United States and Norway, UK-based activists from the alliance told AFP earlier in July.
Global aviation is responsible for around 2.5 percent of global carbon emissions, more than the annual carbon footprint of Brazil and France combined.
Last Generation are known for mounting eye-catching protests -- from throwing mashed potatoes at paintings in museums to glueing themselves on busy roads.
Their tactics, which have proved deeply divisive, have led to some of their members being convicted.
"Instead of seeking tougher sentences, politicians should seriously take the scale of the disaster that they are themselves fuelling," said Lisa Johnson, spokeswoman of the group.
"Prison sentences won't shield us from heatwaves, droughts, floods and dramatically rising sea levels," she warned.
Letzte Generation has said it would hold protests from September 25 against planned government subsidies for Kassel-Calden airport.