The calculated distance (air line) between Rychnov nad Kněžnou and Třinec is approximately 112 miles respectively 180 kilometers.
By car or train, the actual journey to Třinec is certainly longer, as only the direct route (as the crow flies) between Rychnov nad Kněžnou and Třinec has been calculated here.
Air line (approximately)
180 kilometers
97 nautical miles