Complex sentence: There were only three passenger 747-200s delivered to China Airlines, all from 1979-1980, and the other two had been in full passenger service until 1999, when they were converted to freighters.
Split into simpler sentences: There were only three passenger 747-200s delivered to China Airlines, all from 1979-1980. The other two had been in full passenger service until 1999, when they were converted to freighters.