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She flew to Europe via Siberia.
Literal
She [topic-は] Siberia [via-経由で] air-route Europe [to-へ] went.
Two compact spatial ideas chained together: シベリア経由で ('via Siberia') + 空路 ('by air route'). 空路 is a Sino-Japanese compound — 空 ('sky') + 路 ('route') — used adverbially to mean 'by air,' contrasting with 海路 ('by sea') and 陸路 ('by land'). A Cold War-era detail: the Trans-Siberian and Anchorage routes used to be the canonical paths between Japan and Europe before improved range and the geopolitical shifts of the 1990s opened more direct flights. 経由で is the standard way to say 'via': '[place]経由で' marks an intermediate point, distinct from から (origin) or まで (destination). へ here marks direction, slightly more solemn or written-feeling than に for destinations.