BEIJING, March 31, 2008 (AFP) - The maiden flight of China's first passenger airliner has been postponed for at least six months due to delays in the development of key systems, the aircraft maker said Monday.

The first flight of the ARJ-21, initially planned for March, has been put off to September or October, executives of the AVIC I Commercial Aircraft Co. Ltd. told AFP.

This is mainly due to problems with the development of key systems for the plane, they said.

The company is trying to ensure that key systems including the aircraft control system be delivered on time so that the plane can be handed over to buyers in 2009 as planned, said a statement on the company's website.

The 70 to 90-seat ARJ-21 had received 181 domestic orders by the end of March, the company said earlier.

It added that US-based GE Commercial Aviation Services, so far the only publicly known foreign buyer of the plane, has placed firm orders for five and intended to buy another 20.

Although the ARJ-21 is considered an indigenous jetliner, 40 percent of the plane is made by foreign manufacturers, including its engines, according to previous state press reports.