Traffic at airports along Germany's western borders fell in the first half of 2011 because of a new ticket tax, the airport association ADV said Wednesday.

At Frankfurt-Hahn airport, the main German destination for low-cost carrier Ryanair, the number of passengers dropped by 13.7 percent to 1.37 million, compared with the same period in 2010, ADV figures showed.

The Cologne-Bonn airport reported a smaller decline of 1.7 percent to 4.36 million passengers.

Meanwhile the Dutch airport in Maastricht, just an hour by car from Cologne-Bonn, saw the number of passengers soar by 71.8 percent, while traffic at Eindhoven, another Dutch destination, gained 29.7 percent, the federation said.

"The German tax on airline tickets constitutes a definite disadvantage for airports that lie close to the border," the federation concluded.

Overall however, German airline traffic gained 8.1 percent in the first half of the year to 92.6 million passengers.

German authorities hope to earn a billion euros ($1.42 billion) a year from the tax, which ranges from eight euros for short hops to 45 euros for long-haul flights.