Since the transportation costs are caused by the Chinese suppliers' delay problem, I wonder why we are paying more for the delay instead of forcing the suppliers on time (to solve the delay problem). So firstly, I would like to suggest to charge a fine or discount of goods on the delay in transportation. I do not think it is reasonable to delay and solving this problem could lead to a more efficient supply chain.
Then, what about investing in an advanced working-in-process inventory management system? If the company does not have an efficient inventory system, I would recommend to upgrade it instead of using expensive airline transportation. If the system is working well (counting in the occasional delay & order in advance) and we solve the delay problem, then we will never worry about the delay problem. And I would like to change to shipping transportation(if it is cheaper) to save more costs.