By Tom Symonds
BBC Transport Correspondent
Every year around 2 million aircraft land, take off, or pass over in Britain.
Air traffic was hit by the travel slump following September 11
In 30 years' time, though, the government believes there could be two to three times as many planes in the air.
Earlier in December ministers decided to build more runways so the planes can land.
But is there the airspace to hold them?
Last year hundreds of air traffic controllers came out from behind their glowing green screens and headed off to a brand new control centre at Swanwick in Hampshire.
There they settled down in front modern computer terminals and prepared for the future.
Swanwick cost more than £600m, and was built to satisfy our desire to fly. With two or three computer upgrades, it should be able to cope with the growth in air travel for another 40 years.
Before Swanwick, controllers had complained regularly of being 'overloaded', an official term meaning they were coping with too much traffic, with a potential risk to safety.
Since the new centre opened, there have been problems - including several systems failures that left flights grounded - but it's now starting to work better.
IMPACT ON YEARLY PASSENGER NUMBERS
Stansted: From 18m currently to 70-80m after new runway
Heathrow: From 63m currently to 93m when Terminal 5 built, then to 119m in 2015 when third runway built
Birmingham: From 9m currently to 13m in 2011 with runway extension, up to 45m in 2016 with second runway completed
A second air traffic control facility is being constructed at Prestwick in Scotland, largely to handle incoming transatlantic flights.
It will open in 2009, just in time, as flight numbers grow. Two years after that, the new runway at Stansted announced by ministers is scheduled to be complete.
In all, £127m is being spent renovating the entire UK radar system, which will allow controllers to download the flight plans held in aircraft computers.
But there will need to be changes in the air as well as on the ground.
Aircraft move around through airways, ten miles wide, at different heights in the sky.
One of these 'aerial motorways' runs up the spine of Britain, linking controlled airspace around London with that around Manchester.
Just like road traffic on the ground, more traffic in the air will need extra airways through which to travel.
At least the government's new aviation policy did not call for new airports to be built - a relief for officials at National Air Traffic Services (NATS) who would otherwise have had to make major changes to the airway system.
Some alternative plans had envisaged a new airport at Cliffe in North Kent - adding complexity to the airspace over the Thames Estuary, already heavily congested with aircraft making their final approaches to Heathrow.
Some changes will be needed nonetheless, especially outside the South East.
As Newcastle Airport has grown, NATS has had to add an airway linking the controlled airspace around the airport into the national system, and other "regional airports" are now scheduled to grow too.
Busier times ahead at Stansted
Air traffic controllers are given 'sectors' of the sky to look after.
If the number of planes increase, sectors have to be divided in two, so an extra controller can handle the greater workload.
Already the volume of traffic heading towards the London airports over Eastern England has meant new sectors have had to be created.
One place there will have to be changes is Heathrow. It won't get a new runway until 2015 at the earliest, so better use will have to be made of the two existing runways.
At present aircraft take off from one runway, while the other is used for landings, the aircraft arriving and departing in the same direction.
In the afternoon the runways are switched. This means people living at the end of, for example, the northern runway, only have low-flying landing aircraft for half of the day, reducing the amount of noise they suffer.
The government wants to examine proposals for allowing landing and taking off from both runways, which could lead to much more disruption for local people.
But it would also allow more flights to use the airport, which is vital if Heathrow is to cope with extra traffic for the next decade, without a new runway.
Controllers are set to get busier
However, there are worries about the pressure the system is under. In previous years pilots using the airport have complained of receiving late orders to 'go around', or abort a landing, because the previous aircraft was still on the runway.
All in one
But one major development will also help take the pressure off.
The streamlining of air traffic control across Europe is being planned.
This "Single Sky" system will effectively eliminate national boundaries and reduce the need for pilots to contact multiple air traffic control centres.
If all this succeeds, Britain's airways will operate smoothly in future.
If the system fails, however, passengers will know it. Any breakdown in the increasingly complex system will mean planes staying on the ground for safety reasons - and that means growing queues at the check-in.