Extinction Rebellion activists protested at a consultation for the expansion of Luton London Airport at the Nora Grace Hall on Wednesday.
A spokesman said: "They used fun and good humour to get their point across, bringing along Nellie, the Elephant in the room.
"Not on your Nellie! was the main point they were making, and were on hand to chat to people about the problems with flying in general, and other problems specific to the Luton expansion, as well as giving information on where to find the some excellent, low cost options on travelling by train."
An initial consultation was held in summer 2018. Responding to feedback from this, LLAL is proposing sustainable, phased growth of the airport to 32 million passengers per annum (mppa) by 2039, by providing a second terminal north of the runway and extensive new airfield infrastructure.
Also proposed is a third station and extension for the Luton DART fast transit from Luton Airport Parkway station to the new terminal, plus on- and off-site highway improvements.
The climate spokesman added: "As we all know we have to reduce the number of flights we take, if we are to have any chance of averting the climate catastrophe that we are heading for. It was all very good natured, which is what we have come to expect from a Extinction Rebellion event."
Extinction Rebellion (XR for short) wants governments to declare a "climate and ecological emergency" and take immediate action to address climate change.
It describes itself as an international "non-violent civil disobedience activist movement".
Extinction Rebellion was launched in 2018 and organisers say it now has groups willing to take action in dozens of countries.