Proper motion diagrams of the outer Arches fields. Labels are described in Fig. A.1, and for further details see Fig. 8. The larger scatter observed in the Arches proper motion diagrams compared to the Quintuplet proper motions is a consequence of the shallower Arches NACO photometry and mitigated adaptive optics performance. The circles indicate the membership selection criterion as derived from the central field in Fig. 9.