Scheduled drone performances at tourist attractions and events across China have been grounded as the country steps up scrutiny of low-altitude aviation, although in many cases no clear reason was given for the cancellation.Tourist attractions and event organisers in 11 provinces and regions, including Inner Mongolia, Gansu, Shandong, Guangdong and Hainan, took the unusual step last week of announcing that drone shows scheduled from Friday onwards were cancelled. By Monday, none had announced...