Is it safe to fly after having a pneumothorax?

Yes: Don't fly in an open cockpit!

Depends on treatment: Most pneumothoraces can be handled conservatively, either by observation or chest tube placement. The cause of the pneumothorax, outside trauma, is usually a pulmonary bleb, or bubble. If multiple blebs are present, and the pneumothorax has not been handled surgicaly or by chemical pleurodesis, flying is likely a bad idea, as well as diving.

No: Most commercial aircraft are pressurized to 10000 feet and if you had a recent pneumothorax or chest surgery you probably shouldn't fly for at least a month depending on how your condition was treated and the specifics of your problem.

It depends: Patients should discuss their specific circumstances with their physician. It depends on the cause and/or associated abnormality/disease of a patient's lung. Pneumothorax may be caused by chest trauma or from abnormalities in the lung tissue itself. Sometimes, it is recommended that surgery be performed to remove abnormal areas of lung tissue.