Airbus blamed a combination of manufacturing and design flaws for wing cracks on its A380 superjumbo but said it had found a simple solution to the problem, easing concerns among analysts who had feared the issue could dog the European plane-maker. In unusually frank remarks, a top Airbus executive said it had established how to repair the cracks found on a small number of parts inside the A380’s wings, which had prompted European safety authorities to order inspections last week.