Yes, an ascent in a plane can cause a pneumothorax. In this case, the right lung burst slightly in the apex region (weakened by asthma - in some patients the apex is weak due to a congenital pleural bleb). Unfortunately for this patient it was a tension pneumothorax. Every breath he took caused more air to enter the pleural cavity thus increasing the thoracic pressure and decreasing respiratory and cardiac function and eventually causing cardiorespiratory arrest. This raised thoracic pressure also accounts for the bulging veins in his neck. It is a pity that a doctor wasn’t on the flight to drain the pleural cavity with an empty pen casing or something similar.