Cough for about 30 days, chest x ray revealed partially collapsed lung (about 20%). just finished azithromycin. pa at urgent care says i can fly?

Yes: Because of commercial aircraft cabin pressurization systems and 20% or less is involved, it should be ok to fly. Many people with only one lung can fly without problems. You may want to wear a mask to protect your airway from new infections while healing from this one

Hard to say: The general recommendations is to wait 2 weeks after pneumothorax is stable but when did you get pneumothorax? How along ago was the X-ray?