Michael Bernstein, 46, suffered a "medical emergency" while on duty at Philadelphia International Airport Wednesday, according to a statement from the Philadelphia Fire Department.
He was rushed to Mercy Fitzgerald Hospital, where he later died.
All City of Philadelphia flags will be flown at half-staff for 30 days.
"Michael bravely served our city for 22 years and served our country in the U.S. Navy," said Mayor Jim Kenney in a statement. "We are humbled by his dedication, and we will always remember his sacrifice."
Fire officials say funeral arrangements are pending.