CHICAGO, Jan 8 (Reuters) - United Airlines has found loose bolts, so far, on close to 10 Boeing 737 MAX 9 aircraft during inspection, a person familiar with the matter told Reuters. The source said the loose bolts are all in the same location. Earlier, United said it had found bolts that needed additional tightening. However, it did not say how many planes had these installation issues. (Reporting by Rajesh Kumar Singh; editing by Jonathan Oatis)