United Airlines is keeping faith with its core China business despite being buffeted by the country’s trade war with the US, company executives have said.Demand for flights between the world’s two biggest economies has been “weaker than we expected”, the carrier’s president Scott Kirby conceded, and flight schedules showed it had reversed some plans to fly larger planes to Shanghai and Beijing.The Chicago-headquartered company operates 66 flights from the US to mainland China per week, more…