These problems are compounded by the fact that air fleets are getting older: In 1990, 1 of every 4 U.S. airliners was found to be more than 20 years old, and a third of them had been used beyond their prescribed “objectives for useful life ” as originally set by the manufacturer.
ध्वनि समस्याओं के बारे में चिंताओं से कैसे निपटें, इस “मुद्दे पर विश्‍व नागरिक उड्डयन में विभाजन है, ” एवीएशन वीक एण्ड स्पेस टॆक्नॉलजी पत्रिका ने कहा ।