Taiwan carrier China Airlines may invest in the mainland airline industry according to the company’s chairman Ringo Chao. Chao was speaking on the sidelines of a signing ceremony for a cooperative agreement between China Airlines and mainland carrier China Southern Airlines, the South China Morning Post reported. The cooperative agreement, which covers a range of issues from code-sharing to staff training, is another indication of closer relations between the mainland and Taiwan aviation sectors ahead of the commencement of cross-Strait charter flights on July 4. However, analysts warned that any investment by China Airlines in the mainland airline industry is likely still some time away. The company has seen disappointing returns on its investment in Shanghai-based cargo operator Yangtze River Express Airlines while rising fuel costs are threatening its performance in the Taiwan market.