A decline in aircraft orders this year shows the order cycle is peaking after five years of torrid growth, industry experts said on Thursday, raising speculation that Boeing Co (BA.N) and Airbus (AIR.PA) may be forced to scale back higher production rates planned for coming years. “Orders have a history of very high peaks and very low troughs,” said Edmund Greenslet, an independent analyst who publishes the Airline Monitor. With three weeks left in 2015, Boeing Co and Airbus have booked 1,582 orders, a decline from 2,888 in 2014.