Airbus acknowledged Monday it had reinforced the rear fuselage of its superjumbo A380 after problems were detected, but insisted the issue did not cause any further delays in the plane's production timetable.

Airbus spokeswoman Barbara Kracht sought to play down a report in German weekly Der Spiegel on Monday describing troubles with a section of fuselage in the rear cone of the world's biggest passenger plane.

"It is absolutely not abnormal during the development phase of any aircraft that you find you have to do reinforcements here and there," she said from Toulouse, France, where the European planemaker is based.

A "minor" problem was discovered with a section of the fuselage during a trial flight in Toulouse, Kracht said. The fault was fixed in April, she said.

She would not reveal estimates of how much the reinforcement cost or give any other details. Kracht said it did not cause any adjustments in the double-decker plane's production schedule, which has already been pushed back more than a year.

The latest delays, announced last month, sent stock in Airbus' parent company European Aeronautic Defence and Space Co. plunging, led to a management shakeup and angered airlines worldwide that have been awaiting delivery of the A380.

Airbus has sought to soothe investors and customers since then. Markets appeared to largely shrug off the confirmation of the fuselage problems, with shares in EADS dropping just 0.5 percent Monday to 20.97 euros ($26.59).

Der Spiegel said internal Airbus documents showed that at the beginning of March, the company decided to strengthen the problematic fuselage — resulting in extra costs and extra weight. The report did not elaborate on the problems.

In 2004, Der Spiegel was the first to reveal that the A380 was overweight, leading to major cost overruns.

Despite the problems, the A380 won a new show of confidence last week at the Farnborough International Airshow, as Singapore Airlines said it would exercise an option to pick up nine more of the planes. Singapore Airlines is to expected to put the first commercial A380 in the skies, with its first delivery expected later this year.

The air show gave Airbus overall a welcome boost in its battle with rival Boeing Co. for customers.

Airbus won orders or commitments for 182 planes valued in total at $21.5 billion at the event. Chicago-based Boeing (BA) said it had booked 75 orders and commitments, worth an estimated $9.65 billion.

Airbus has sold more planes than Boeing for the last five years but that looks set to change this year, despite the results of Farnborough.