Fifteen climate change activists have been arrested at London Southend Airport.
Members of Plane Stupid and Climate Rush entered the airport at 09:00 BST and were apprehended by officers.
In a press release, the groups said they planned to put solar panels on the runway and do a dance routine dressed as pilots and cabin crew.
Police initially said 16 people were in custody, but at 15:00 BST confirmed five men and 10 women were detained.
The airport wants to extend its runway by 300m (984ft) to allow larger passenger aircraft to be used.
The Stobart Group, which owns the airport, aims to have two million passengers a year passing through its terminal, by 2020.
In a statement before the arrests, a spokeswoman for the protesters said: “Southend Council say the expansion will bring jobs.
“But investment in renewable energy would create many more jobs without damaging the climate.
“What we need is solar power, not plane power.
“The bigger runway is bad for climate change, bad for local residents under the flight path and is not needed to help the local economy.”
Using Twitter, Plane Stupid said members had invaded the runway at 09:00 BST and remained there “for at least an hour”.
Essex Police said officers responded quickly to reports of protesters gaining access to Southend Airport shortly after the protesters broke in.
All 15 suspects are being held on suspicion of entering a restricted zone at an airport and aggravated trespass.
A 20-year-old man and a 19 year-old woman from Norwich and a 43 year-old man from Whitstable in Kent are among those arrested.
The remainder are from various parts of London.
Det Ch Insp Stuart Hooper said: “We were on heightened general alert to airports and our response to the protest was very swift.
“We have a number of well-rehearsed contingency plans for events such as this and we have launched a criminal investigation following the incident at Southend.”
An airport spokeswoman confirmed the runway had been closed for a “short period” while police dealt wth the situation.
“No flights were impacted by this event,” she said.