Who is subject to mandatory retirement under FERS?
Mandatory retirement primarily applies only to employees in what are called “special groups,” the large majority of whom are firefighters, law enforcement officers or air traffic controllers.

Firefighters and law enforcement officers generally are subject to mandatory retirement at age 57 with at least 20 years of covered special group service. An agency head may retain a law enforcement officer until age 60 if the LEO's continued service is in the public interest. A FERS LEO may be retained beyond age 60 with the permission of the President.

An air traffic controller must be separated from service on the last day of the month in which he or she becomes age 56.