BEIJING/SYDNEY (Reuters) -China’s “Big Three” state airlines pledged on Friday to buy a total of almost 300 Airbus jets, the biggest order by Chinese carriers since the start of the COVID-19 pandemic and a breakthrough for Europe as Boeing remains partially frozen out of China. In apparently coordinated announcements, Air China and China Southern Airlines said they would each buy 96 A320neo-family jets worth $12.2 billion at list prices. China Eastern Airlines said it would buy 100 airplanes of the same type, worth $12.8 billion. Airlines typically receive substantial discounts to list prices …