Parts availability. Shop timelines. Example: Phenom 300 hot section inspection, they found some issues. Parts needed to fix the plane from Pratt and Whitney are on back order, P&W won’t give a timeline for when we’ll get them. Owner has JSSI loaner engine coverage for this exact hypothetical issue, they don’t have enough loaner engines, we were only given a loaner engine for 4 weeks (plane has been down for almost 4 months now). Once parts arrive, we are airplane number 6 in line to get the work completed at the shop. It’s difficult to manage owner expectations and frustration when you can’t give a timeline for work completion or another loaner engine.

Another frustration can be repeated related AOGs. Owner will say “I thought we fixed that?”.