All airliners occasionally have problems with wheels and/or tires. And occasionally have cracked window glass. And occasionally have engine failures. And occasionally have pressurization problems, Read avherald.com for a few days and you'll see that it happens to Airbus, Boeing, Embraer, Bombardier, and others. And with the number of flights worldwide, some kind of problem serious enough to cause a return to the aiport or diverting to an alternate happens almost every day.<p>Boeing has some serious questions to answer about their engineering and QA processes. But attributing random normal problems to that just confuses the issue.