By City AM reporter Boeing expects delayed suppliers to catch up on parts that have slowed production of its 787 jets to below a rate of five a month, as the U.S. planemaker works to restore output of two key commercial programs by the year’s end. Boeing and its European rival Airbus are struggling to meet strong airline demand for jets as they wrestle with problems within their supply chains and factories. Such concerns are set to cast a shadow at the Farnborough Airshow from July 22 to 26, despite strong travel demand. Earlier this year, Boeing lowered 787 output to allow “suppliers to catch…