If a person is working as a United States military air traffic controller and then they get discharged, do they have to go through additional training and tests to work as a United States civilian air traffic controller? or do they just get hired, without any additional training and tests?
Wasabi's answer is not correct, or at least not fully correct. You actually ask two questions: does a military controller need to take additional tests and training to get hired, and do they need additional training to work as a civilian controller. The answers, respectively, are "no" and "yes."
The hiring practices change every so often, but here's how it is now:
"Off-the-street" FAA controllers receive training at the FAA Academy in Oklahoma City. This training starts with Air Traffic Basics and continues to Initial Tower Cab (for Terminal-track new hires) or Initial Enroute (for Enroute hires). New hires do not go directly to standalone TRACONs anymore. People who graduated schools in the Collegiate Training Initiative do not have to attend Basics but do attend Initial.
In order to get to Basics, new hires must take the ATSA aptitude test, as well as undergo medical and security investigations.
After graduating the Academy, new trainees are sent to their field facilities and go through classroom and simulator training before eventually progressing to On-The-Job instruction (plugged in working live traffic alongside a trainer who retains ultimate responsibility for the control position). Any controller, even one who has been previously certified at an FAA facility, must go through this facility-specific classroom/sim/OJT progression any time they transfer to a new facility.
Prior-experience new hires (who mostly come from the military) may elect to go through the off-the-street hiring process if there is a bid open at the time they are discharged. But usually they apply though a separate bid that is only open to prior-experience controllers. This bid allows them to be placed directly at a facility that should, in theory, correspond to the type and level of their prior experience; this is almost always a Terminal facility (tower, up/down, or TRACON) but an Enroute facility may be offered very rarely.
If necessary these new hires may be sent to the Academy for training, for example if they only worked radar before but were assigned a tower facility, but for the most part they enter the training process at their new facility immediately. This process is not waived just because they have previous experience. They do benefit by not having to take and pass the ATSA aptitude test, however.
As far as "tests" go, in the FAA, there are annual or biennial "refresher" simulator problems and "skills evaluations" where a supervisor does a limited checkride with the controller to ensure they don't need additional training in any area. But this is based on when the controller certified at their facility and has nothing to do with any tests they might have done in the military.
No. A US military air traffic controller does not need additional testing nor training to become a civilian air traffic controller. This is because the testing and training for military Air traffic controllers follow the same basics as civilian air traffic controller testing and training, but with additional requirements, training, and testing to fit the needs of the military. Any test given for a civilian air traffic controller is also taken by a military air traffic controller. An air traffic controller needs to retake tests each year, whether they are a civilian or a military air traffic controller. So as long as the discharged military air traffic controller applies to become a civilian air traffic controller within 1 year of his/her last test, he/she can become an air traffic controller without any additional testing or training whatsoever. But, once a year has past since his/her last test, they must retake the tests. But when they retake tests, they only need to retake civilian air traffic controller tests, and not military air traffic controller tests. This is because they aren't working as a military air traffic controller anymore.
If a Military Air Traffic Controller is looking to be hired as a civilian air traffic controller because they were discharged from the military due to being 31 years or older; they can apply to be a civilian air traffic controller even though they are 31 years are older, because of FAA's Phoenix 20 program. This program allows them to work past the age of 31, and it can also allow them to continue working for the military before moving to the FAA to continue air traffic control as a civilian air traffic controller, according to https://www.govinfo.gov/content/pkg/GAOREPORTS-GAO-02-591/html/GAOREPORTS-GAO-02-591.htm So, a Military Air traffic controller does not need to retake tests before become a civilian air traffic controller unless they have not retaken tests in 1 year since the previous test retake.