I had 2 spontaneous pneumothoraces 4 years ago and had a pleurodesis with doxycycline. Is it okay to fly to Hawaii?

Interesting. Assuming you don't have BHD syndrome, and that you didn't have multiple blebs on any of your exams, it's probably quite safe...most planes are pressurized to 8000 feet or less. If you had lots of blebs detected on your studies, those might still cause a problem if the plane lost pressure suddenly, but otherwise 8000 shouldn't be a problem.