Easyjet has said it will create 2,500 jobs and more than double its presence at London Luton Airport if expansion plans are approved by the government.
The firm wants to increase passengers from four million to nine million a year and add more destinations.
But chief executive Carolyn McCall said the plans were in-part reliant on improvements at the airport being made.
A campaign group said it wanted evidence Easyjet would commit to quiet engines and avoid night flights.
At the end of last year Luton Borough Council approved increasing airport passengers from 10 million to 18 million a year, but the decision is currently being reviewed by Communities Secretary Eric Pickles.
