ZHUHAI, China (Reuters) -COMAC said on Tuesday that Air China (OTC:) was the first customer for the Chinese planemaker’s C929 widebody aircraft under development that is designed to compete with twin-aisle models from Airbus and Boeing (NYSE:). COMAC’s deputy director of marketing, Liu Yan, made the announcement at China’s biggest air show in Zhuhai. Liu did not disclose the number of aircraft that Beijing-based Air China would purchase or planned