Climate change campaigners are to mount a protest at plans to redevelop Carlisle Airport.
The existing runway at the airport dates back to the 1940s
Stobart Air Limited wants to invest £25m in a rebranded Carlisle Lake District Airport, to increase freight and passenger flights.
County Council bosses and the area's regeneration agency have backed the move, but Carlisle City Council has yet to make a final decision.
South Lakeland Action on Climate Change fears the environment will suffer.
The revamp plans include the construction of a new £30m runway, passenger terminal, air traffic control centre, hangars, office buildings, distribution warehouses and car parking facilities at the site of the existing airport.
The existing runway dates back to the 1940s and is only able to handle limited traffic.
But campaigners fear the plans could attract large passenger aircraft and pose a risk to the environment.
Sonny Khan, from the campaign group, said: "There are parts of the planning application which lead us to believe that they are building an airport capable of aircraft as big as 737s or 747s.
"If you look at the terminal building, this is a very large building of four floors and 50,000 sq ft and seems much larger than that required to service the passenger numbers they are talking about.
"There has been no master plan published and we really need to know what they are planning for the future."
A spokesman for Stobart Air's Carlisle-based parent company, WA Developments, said all the necessary procedures for the planning application had been followed.
He said it was now up to Carlisle City Council to make a final decision.