Quality issues at Boeing (BA -4.58%) are wreaking havoc on the aerospace giant's customers, causing airlines to rethink their growth plans. Shares of Southwest Airlines (LUV -14.52%) were down 14% as of 11:30 a.m. ET after the company said it was trimming capacity and reevaluating its financial forecasts for the year.No planes, no growthBoeing investors have been taken on a turbulent ride in recent years, and the company's customers have not been treated much better. Boeing has been plagued by design and qu ...