The calculated distance (air line) between Thornaby-on-Tees and Milton Keynes is approximately 174 miles respectively 279 kilometers.
By car or train, the actual journey to Milton Keynes is certainly longer, as only the direct route (as the crow flies) between Thornaby-on-Tees and Milton Keynes has been calculated here.
Air line (approximately)
279 kilometers
151 nautical miles