Engineers at European planemaker Airbus are battling problems in stress tests for the new A380 superjumbo, Germany's Der Spiegel magazine has reported.
There were "unexpected and significant difficulties" with the rear end of the plane when tests were carried out on it, the magazine quoted an insider as saying.
The landing gear is also causing engineers concern, the magazine reported, adding that the A380's first flight in March could be delayed by weeks.
An Airbus spokesman said the stress tests were heading in the right direction within the company's expectations, Der Spiegel said.
Airbus could not immediately be reached for comment.
The A380, which is the world's biggest civil aircraft and was formally unveiled in Toulouse, in France, last month, can seat between 555 and 850 passengers and has a list price of between USD$200 million and USD$250 million.