The owners and operator of London Luton Airport say they are now in "absolute agreement" over expansion proposals.
Operator London Luton Airport Operations Limited (LLAOL) had submitted a rival proposal to airport owners Luton Borough Council.
But it has now issued a "revised masterplan" which shows an increase in passengers from 10 to 18 million per year.
The plan also predicts a 40% increase in aircraft movements.
A planning application is due to be submitted in November.
London Luton Airport, the UK's fifth biggest, is owned by the council under the name London Luton Airport Limited (LLAL).
In January, the council revealed proposals to boost passenger numbers to 18 million per year, but in March, LLAOL said 15 million was more realistic.
However, in June the two sides agreed to merge the plans in order to move forward.
The plans also include additional taxiway and aircraft parking facilities and a multi-storey car park located on part of the existing short-term car park.
LLAOL said it now agreed with LLAL that the airport could cope with 18 million passengers after a review of feedback and "a process of detailed modelling and environmental assessment".
Managing director Glyn Jones said: "It's a relatively small change to what we were putting forward before but an important one because it is based on absolute agreement."
He said it estimated an increase of aircraft movements from 112,000 in 2012 to around 157,000, and confirmed any increase in capacity would take place within the existing boundary and use the existing runway.
"We have a relatively small land-bank so we will be building a little bit more but we will really be re-using a lot of what we have already got," he said.
He also said they would put forward a package of measures on noise management and will look at "road access issues".
Those opposed to expansion said the airport was "already running at twice the planning consent levels it got in the late 1990s".
John Davis from Luton and District Association for the Control of Airport Noise (LADACAN) said it would challenge the plans.
He said: "Enough is enough and we think it would be much better if it was content to run as it is without taking on this massive increase."
If the planning application goes through, building could start in winter 2013.