Boeing Shares Could Fall 15% if Sales Slow by Reuters @FortuneMagazine May 22, 2016, 2:35 PM EDT E-mail Tweet Facebook Linkedin Share icons Boeing Co’s stock could fall as much as 15% if sales of its aircraft fall on weakening demand, according to a report on Sunday in the financial publication Barron’s. Airlines and leasing companies are using planes longer and delaying orders for new aircraft, the publication said. Low oil prices have also reduced the need to buy updated, more fuel-efficient planes, it added. Boeing BA generates roughly two-thirds of its revenue from commercial aircraft, and the remainder from its defense business. Demand for Boeing’s 737 planes remains strong despite competition from Airbus Group SE AIR and Bombardier Inc . However, its 777 and 787 models are at greater risk, Barron’s said. Boeing’s 787 could face write downs because initial costs were high and sales have slowed, it added.