I was trying to buy a RT HKG-PEK flight, and found that CX is selling them at a price of HKD $4500+ (Fare Class M). However, CA (Air China) is selling the same tickets (although they are under CA's flight numbers) for about HKD $3000 (Air China's Fare Class V). Are there any downsides if I purchase the tickets from CA? I should be able to earn MPC and Asia Miles credits just as if I were flying a V-Class ticket on CX, right?