I read the entire article hoping to find some mention of the air recycle rate on the planes ... which is typically a 50/50 mix of recycled cabin air and outside

I read the entire article hoping to find some mention of the air recycle rate on the planes ... which is typically a 50/50 mix of recycled cabin air and outside, fresh air. It seems like very low hanging fruit to decrease transmission rates by increasing the ratio of fresh air to recycled cabin air ... perhaps there are technical challenges associated with that ?