(Reuters) - Demand for global air freight rose for the fifth straight month in August as European airlines benefited from an increase in German export orders, the International Air Transport Association (IATA) said on Wednesday.

Freight demand, measured in freight ton kilometers (FTKs), rose 3.9 percent year-on-year for the month. Demand at European airlines grew 6.6 percent.

"August numbers showed improvements in cargo demand. While this is good news, the underlying market conditions make it difficult to have long-term optimism", IATA head Alexandre de Juniac said.

Available capacity rose 4.1 percent for the month and load factor fell by 0.1 percentage points to 40.8 percent.

Middle-Eastern carriers saw freight demand growth of 1.8 percent -- the slowest pace since July 2009.

(Reporting by Anna Serafin; Editing by Thyagaraju Adinarayan)