That’s the main feature of today’s Update 1.87, “Locked On!” which adds “a sensor system, that will consist of means for radio detection and target lockon, as well as means for finding firing solution for airborne armament.” Different vehicles have different capabilities, but the overall intent is to make things a little easier for ground vehicles when faced with airborne targets, mirroring the actual historical development purpose of radar. You can learn more about the system here.
This update also adds a bunch of new vehicles, including seven new tanks, 11 new aircraft, two new maps, and six new helicopters. Another confrontation map, Vietnam, has been added for aircraft and helicopters, as well as a slew of other changes. Read all about those in the patch notes on the War Thunder site.