Hi Joseph,
Think about your work as an aircraft mechanic in terms of process groups: Initiating, Planning, Executing, Monitoring and Controlling, and Closing.
Did you ever participate in planning maintenance schedules or deciding when and how to undertake major repairs or upgrades? Did you create or contribute to maintenance plans, allocate resources, or plan for contingencies? and so on... This approach could help you describe your work in terms of project management activities.
Also, check the information on PMI website:
www.pmi.org/military/#:~:text=PMI%20cate...ement%20(CAPM)%C2%AE
.