Application of AS9110

Answer:
While AS9100 Rev D applies to any manufacturers in the aerospace industry (specifically Aircraft, Space and Defense organizations). AS9110 is specifically for aviation maintenance organizations, precisely for organizations that do repair and overhaul for the aircraft industry. This standard is for companies that take parts from aircraft, such as motors, and repairs or overhauls them to make them work again. It is not for standardized repairs of a company’s own products as part of a customer return scenario.
So, you are correct, unless a customer or legal entity specifically requires that a company is AS9110 certified, this may not apply to you. If you do overhaul functions for aircraft electronics you may wish to investigate this standard for these operations, but not if you are strictly fix ing customer returns, and certainly if you are not in the aircraft portion of the aerospace industry.
For more on the differences, see the article: How does AS9110 & AS9120 relate to AS9100 Rev D?, https://advisera.com/9100academy/blog/2017/10/30/how-does-as9110-as9120-relate-to-as9100-rev-d/