All FAA air traffic control supervisors are former controllers, it's just the way things work and it's no big deal. Nearly every controller will give management a try at some point during his career, and luckily the FAA allows you to return to your atc duties if management turns out not to be your cup of tea. But back in 2008 the union was angry about what they considered poor negotiating from the FAA on a contract back in 2006 so at the bi-annual NATCA convention the union voted to strip seniority away from any controller who left the bargaining unit between 6/6/06 and 9/20/08 and then returned to the unit. 7 of the 137 people harmed by this attack filed a ULP against the union. After losing many rounds, and appealing with dues payers money each time, the union finally lost the final decision by the three member Federal Labor Relations Board on Feb 13th of this year. At the union's convention held in late March they voted to give the seniority back to those wronged in an attempt to make it look like they were doing the right thing.
This has been a very divisive issue among air traffic controllers for nearly four years with many quitting the union in protest of its childish actions. Hopefully with this episode behind them there can be a little less animosity and open hatred in ATC facilities from this point on.