Engineers inspecting Airbus A380 aircraft for cracks on a part inside the wings have found similar flaws on at least one aircraft, industry sources said on Tuesday.

European safety authorities ordered urgent inspections on just under a third of the superjumbo fleet last week after two types of cracks were discovered on a bracket inside the wings of the world's largest jetliner.

Cracks have been found inside the 9,100-square-foot wing of at least one of the superjumbos examined under last week's directive, industry sources said.

They also said cracks on another part of the wing were discovered two years ago. The problem was documented at the time but attention has not focused on that incident until now.

Airbus insisted on Tuesday this was a different issue from the latest flaws and had been resolved. European safety inspectors reacted to the earlier problem by ordering checks in October 2010, a month before an engine blowout severely damaged a Qantas A380 and triggered global headlines.

It was during $130 million repairs -- lasting more than a year -- to that airliner in Singapore that the latest type of crack was discovered. This in turn has led to the discovery of another and potentially more significant type on the same part.

Airbus and safety authorities are stressing the 525-seat airplane is safe to fly as engineers check wings for more tiny cracks in a type of wing bracket known as rib feet.

CONSTANT EVALUATION

The checks affect some 20 aircraft operated by Singapore Airlines , Dubai's Emirates and Air France , making up just under a third of the current A380 fleet.

Airlines have until Friday to complete a first phase of tests after which Airbus or European safety authorities are expected to give an update on any new findings.

Airbus declined to comment on any interim results while airlines carry out checks under the timetable established by regulators.

But a spokesman said recent events showed the industry's process of continuous evaluation, designed to catch and repair any faults before they become a hazard, was working smoothly.

We have clear evidence that the airworthiness process is working, a spokesman for the EADS subsidiary said.

An issue has been found, we reported it, we made a recommendation to our customers, EASA made it mandatory and the and the inspection and fix if necessary are both under way.

Both Airbus and Boeing are subject to a stringent safety regime that involves a continuous process of inspection and repair, governed by airworthiness directives from EASA or the U.S. Federal Aviation Administration and usually both.

In practice the directives frequently formalize actions already recommended by the manufacturers' service bulletins.

Safety experts can chart the number of directives to tell whether an aircraft is affected by more glitches than normal. A new aircraft will tend to develop more directives as a result of teething problems and an older type of aircraft will attract extra attention due to metal fatigue, with a plateau in between.

An EASA spokesman said the A380 was producing fewer safety issues than a normal aircraft of its age.

Airbus is however keen to avoid any further embarrassment and to allay concerns over its flagship aircraft. The UK-designed and -manufactured wings are the largest ever developed for a civilian passenger jet.

The A380 was developed in France, Germany, Britain and Spain at an estimated cost of 12 billion euros to compete with the Boeing 747 and establish Airbus as a challenger at the top end of the market but has hit a series of production delays.

Airbus has sold 253 of the aircraft and 68 are in service.

(Reporting by Tim Hepher, Editing by Dominique Vidalon and Jodie Ginsberg)

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