Google Earth version 5.1, originally released in late 2009, remains a milestone in the history of virtual globes for its focus on performance and "under-the-hood" stability. While modern versions like Google Earth Pro are now the standard, some users still seek version 5.1 for its low system requirements and classic interface.
Building on the massive content updates of version 5.0—which introduced and Google Ocean —version 5.1 was primarily a performance-focused release designed to make "flying" feel more fluid. Google Earth 5.1 is now out of beta - Maps google earth version 5.1 download