Chief executive Paul Kehoe told a meeting of the airport's consultative committee that further work is needed before plans are submitted, following British Airways' withdrawal from the airport and the launch of services by Ryanair.
Local pressure group Stop Bristol Airport Expansion called for clarification. It said the masterplan, published last year, predicted 6.6 million passengers a year by 2010, but seven million are expected in 2008 alone. The group said it will advise supporters to respond to local core strategy consultations.
An airport spokesman said the figures in the masterplan are based on the best market information available.