FRANKFURT, Germany (AP) _ From sushi bars to sex shops, Frankfurt Airport offers travelers plenty of ways to occupy their time before flying.

Yet there may be demand for even more: Nearly half of last month's flights to and from the airport were delayed at least 15 minutes and some were hours late.

The tardiness is so severe that Lufthansa AG has begun keeping three jets with crews on standby here just to fill in for flights that are seriously delayed. All three replacement jets have been busy, the airline says.

In skies across Europe, unprecedented numbers of passenger flights are overloading the region's fragmented air traffic control system.

A surge in flights packed with vacationers heading for the Mediterranean has added to the strain. Holiday travel increased just as the skies were clearing of disruptions caused by NATO's spring offensive in the Balkans.

``We have once again reached a crisis situation,'' said Emanuela Petracchi, a Geneva-based spokeswoman for the International Air Transport Association, an airline trade group.

Similar problems in the United States have contributed to a doubling of delays and cancellations by U.S. airlines over the past year.

At airports in 32 European countries, airline deregulation and cheaper fares helped boost the number of passenger flights to more than 734,000 in July, a 17.6 percent increase from three years ago. Delays due to air traffic problems have risen even faster, 33.5 percent in the same period, IATA says.

In Spain, a shortage of air traffic controllers caused delays earlier this year, and a strike by baggage handlers affected flights to the Canary Islands, a popular tourist destination.

Flights to Switzerland and southern France suffered delays after the French, fearing potential job losses, halted efforts to reorganize control of the airspace along the Franco-Swiss border, Petracchi said.

By the end of July, delays topped the list of complaints by passengers in Europe, said Hans Krakauer of the International Airline Passengers Association, a consumer group based in London.

Other passenger gripes? Poor service on the ground and in the air, including cramped seating and dirty rest rooms.

``If you have a very filthy toilet ... and if you point that out to a cabin attendant, the usual reply is, 'What do you want us to do about it?''' Krakauer said. ``The passenger is getting a lousier deal.''

Delays have been most severe at Milan's Malpensa Airport, where 75 percent of all departures and arrivals were late in the April-June quarter. Barcelona and Madrid fared almost as badly, while Scandinavian airports had the most-punctual flights, according to the Brussels, Belgium-based Association of European Airlines.

For Frankfurt to suffer widespread delays shows just how bad the situation has become.

Flughafen Frankfurt/Main AG, the busiest airport in continental Europe, long prided itself on its efficiency. Yet delays here grew from 30 percent of all departures in the first quarter of the year to 36 percent in the second quarter. In July, 48 percent of all departures were delayed.

Aviation officials blame most of the problem on air-traffic bottlenecks elsewhere in Europe _ something over which Frankfurt has little, if any, control.

A charter flight from Frankfurt to Adana, Turkey, was one of several to suffer delays on a recent afternoon. The reason: last week's earthquake in Turkey.

Feryat Nural, 27, tried to amuse his two bored children while waiting for the flight to be rescheduled.

``Here, it's like I'm in prison,'' the Turkish metalworker said, pointing out that the airport's 180 shops and restaurants were too pricey for his pocketbook.

The main obstacle to timely fights in Europe is the region's poorly organized airspace _ a patchwork of zones managed by 65 different air traffic control centers using 35 different monitoring systems.

Aircraft often must adjust their speed, course or altitude each time they enter a new air traffic control zone. Many countries also make passenger planes fly around airspace reserved for their military aircraft.

Lufthansa, which is headquartered in Frankfurt, says its jets have used up $16 million worth of fuel this year just to make such adjustments. The airline also must absorb the cost of operating its three reserve jets and crews.

Air France has put the cost of delays this summer at around $350,000 a day.

Airlines and airports blame Europe's disjointed flight control network on politicians intent on jealously guarding sovereignty over national airspace at the expense of Eurocontrol, an agency in Brussels that supervises regional air traffic.

Eurocontrol can propose ways of integrating the various air traffic control systems, but European governments have denied it enforcement power.

``They created an artificial currency called the euro,'' said Frankfurt airport spokesman Klaus Busch. ``So why can't they do something in the air traffic business?''