But the huge scheme has been put largely on hold as a result of the recession. Parts of the work have been carried out and now the airport is planning to extend its terminal building.
Other improvements will eventually include a new hotel and a new public transport interchange.
At the moment the airport deals with around six million passengers a year and the aim is to increase the total to ten million.
A brand new £6.5 million central walkway which is designed to ease congestion at peak travel times has just been completed.
And the extension of the terminal building is expected to be finished by summer 2015.
The new walkway has space for four pre-boarding zones serving six departure gates and has been designed to take into account the latest generation of twin-engine, wide-body jets, such as the Boeing 787.
It is hoped that the new generation of jets will allow people to fly from Bristol direct to long-haul destinations in Latin America and the Far East.
Construction of an eastern terminal extension will begin in September.
The £8.6 million project is the first major expansion of the terminal building since it opened in 2000.
The development is expected to lead to the addition of more shops and create more space for existing retailers.
It will also see the installation of hundreds of additional seats in the departure lounge and include a second executive lounge facility. Behind the scenes, it will deliver an improved baggage processing area, while other features including an outdoor terrace for passengers.
Airport chief executive Robert Sinclair said: “The central walkway sets a new benchmark for passenger facilities at Bristol Airport and the eastern terminal extension will raise the bar higher again.
“This significant investment demonstrates our ambition to become the airport of choice for passengers across the South West and South Wales.
“High quality infrastructure will also make Bristol Airport even more attractive to airlines, helping to extend the choice of destinations available – including long haul services to North America and the Middle East in future.”
Other improvements in recent years include a second immigration point, additional security search channels and three new aircraft stands.
Bristol Airport is the UK’s fifth largest airport outside London and the ninth largest in the UK, handling 6.1 million passengers in 2013.