I have an upcoming flight on BA55 (evening A380 service LHR-JNB). It seems to be delayed more often than most. Presumably, the delays are often due to the aircraft arriving into LHR late. Does the aircraft used for this flight always or usually come in from the same place and if so, where? It would be useful to be able to track that flight to get an early heads up on whether to expect an on-time departure. Thanks