In the upcoming "Rzhev" update, all radio operator class soldiers will gain access to a new radio command - Supply crate drop. A transport plane will deliver a crate full of the ammunition to the location you choose. For resupplying allies, the soldier who called the supply drop will receive additional battle score. This command has a 30 second cooldown.
One call, and your whole team will be grateful. Let the engineers get their hands dirty with construction.