Climate justice campaigners—including one dressed as a polar bear—chained themselves together on the runway of London's Heathrow Airport early Monday morning, forcing flight cancellations and delays to creatively protest the proposed expansion of the facility.

"No third runway! No ifs, no buts!" chanted the 12 protesters, who hail from the direct action organization Plane Stupid, a network of grassroots groups that opposes aviation expansion out of concern for the environment.

The group's Twitter feed shows the locked-down activists, who launched the protest at 3:30 AM and held the runway for hours, smiling even as police proceeded to dismantle their lock down with machinery.

Tweets by @planestupid

According to the Guardian, all 12 protesters were eventually arrested and 22 flights forced to cancel.

The direct action came less than two weeks after the UK's Airports Commission recommended the construction of a third runway at Heathrow, despite widespread concerns about the pollution and carbon footprint that would result.

The push for a new runway comes despite Prime Minister David Cameron's pledge in 2009, before he took office, that "The third runway at Heathrow is not going ahead, no ifs, no buts." Yet, in office, Cameron set up the commission to examine the airport's expansion.

Heathrow Airport has long been a site of struggle against the government's role in propping up the airline industry despite its harmful impact.

In a statement responding to the commission's report, Plane Stupid declared: "We cannot meet our climate change targets and build new runways at the same time. It's a choice between the two. This should be very simple to understand."

"Nine of the ten most popular destinations out of Heathrow are short-haul including to places such as Manchester and Paris. There are already very good existing rail alternatives that we should be using instead," the group continued. "15% of the UK population take 70% of the flights. Building new runways will only benefit rich frequent flyers who are burning the planet for unnecessary leisure flights."

"We thought we’d won this fight, because David Cameron said 'no ifs, no buts' there would be no runway at Heathrow," Sarah Shoraka of Plane Stupid told the Guardian. "We thought it was off the table and then the report came through and we thought: 'We’re going to have to fight this all over again.'" 

"We picked the spot so we wouldn’t endanger flights trying to land," Shoraka continued. "But we are not big corporations, we are not Boris Johnson, we don’t have resources at our disposal other than our bodies."