Long-awaited F-16 fighter jets are set to be flying in Ukraine within weeks, but Ukrainian and Western officials now caution that the aircraft, once championed by Kyiv as a game changer, are unlikely to make an immediate impact on the battlefield, where Russia is slowly advancing.

There are simply too few of the planes and too many Russian air defenses that can shoot them down. That means the first F-16s will probably serve to boost Ukraine’s air defenses — to shoot down aerial targets such as missiles, drones and aircraft — rather than strike Russia’s invading ground forces and other military assets near the front.