LONDON -- European skies are overcrowded, and the problem is only getting worse.
Air traffic has increased by an average of 7.4 percent a year for the last two decades. One flight in four is delayed by air traffic control problems, according to the European Union's transportation website.
But if you think being a passenger is bad, try being a pilot. Airspace over Europe is divided into a patchwork of national systems, which are all controlled separately.
A two-hour flight from Rome to Brussels, for instance, must pass through nine different control centers.
When a plane makes the transition from one system to the next, the pilot must dial a different frequency and complete a lengthy radio transmission called a handover. Not only that, but different countries have different regulations, so that a plane may have to climb or descend en route simply to stay within controlled airspace (PDF). If the controller in the next system is too busy, then the plane has to wait outside that controller's airspace (or on the ground) for its turn to enter.
None of this has anything to do with operational efficiency, flight safety or pilot workload, but it is the main reason for the delays.
"Traffic in and out of the U.K. will double in the next 12 years," said Richard Wright, a spokesman for Britain's National Air Traffic Services. "Despite the downturn in long-haul since Sept. 11th, there is a rapid growth in intra-European travel driven by the low-cost carriers like easyJet and Ryanair."
A technique known as "reduced vertical separation minima," which cuts vertical spacing between aircraft to as little as 1,000 feet, has increased the amount of traffic that can occupy the same bit of sky, according to the European Reduced Vertical Separation Minimum Programme. But packing more planes into the same airspace is only a stopgap measure.
The long-term fix is to install digital data links between controllers and pilots.
"In busy sectors like Maastricht, 50 percent of controllers' time is spent on handovers," said Tony Whyman, an industry expert from Helios Information Systems.
A system called VDL2 (VHF Data Link 2) can digitize this exchange and, eventually, other routine interactions between pilots and controllers like flight level clearances and trajectory planning.
In effect, it moves air traffic control from a serial model to a parallel one. Today, one controller manages an entire sector because only one person at a time can speak on a given radio frequency. With VDL2, several controllers can monitor the same sector and handle routine instructions using the data link.
"There is a definite shift these days from voice to data; however, the system should allow for both," said Victor Aguado, director general of Eurocontrol, the organization charged with harmonizing Europe's air traffic control system. "If routine communications are processed automatically, then voice can be kept for unusual circumstances and situational awareness."
He said experiments so far indicate that using such a system would reduce delays by more than 40 percent due to a reduction in workload for air traffic controllers.
But there's a problem: Only around 20 aircraft in Europe have VDL2, and at least half the European fleet needs to be equipped before any improvement happens, said Whyman of the Helios Institute.
And, added Whyman, there's no real incentive to be an early adopter and see a rival airline get the benefit without paying anything.
So, the problem may require a political solution.
Eurocontrol is set to make VDL2 mandatory by 2010. More importantly, the European Union is pushing for a "single European sky," which, in more prosaic terms, means consolidating national control zones into a smaller number of rationally planned airspace blocks. At present, only one -- centered in Maastricht, Holland -- is operational, but a second is due to come online soon. While some countries resist ceding control of their airspace, others, including Britain, are supportive -- and any consolidation will make it easier to roll out new technology like VDL2.
Wright, of the National Air Traffic Services, said his organization "believes that the sort of significant change that will enable European service providers to meet future demands for air traffic can only come from an international initiative such as single European skies."
