Earlier this year, a deal was reached and Lockheed is once again delivering the F-35. However, the Technology Refresh 3 (TR-3) upgrade is only sufficient for these fifth generation fighter jets to be used as training jets – they will modified later to be combat-worthy. But what is the TR-3 update, and what difference does it make? The first F-35 to fly with the TR-3 update installed took place on January 6. However, it has been anything but plain sailing since then.