Defenders of Berk
It was first tested by Hiccup Haddock III and Fishlegs Ingerman using Terrible Terrors. Hiccup used Sharpshot as it's first courier to notify Fishlegs of the Screaming Death and it's sinking of islands in it's search for it's mother. Hiccup also use it to send a message to his riders to bring the Screaming Death to Outcast Island.
In Race to the Edge
Three years after The Berserker War, Heather used to maintain contact with Trader Johann during her raids on ships and Dagur. Stoick then used it to notify Hiccup of Dagur's attack run on Berk. Trader Johann then used one to ask for help in saving his ship from Scardian's pack of wild dragons near Forest Island. At the same, Astrid then asked for help from Berk in defending Dragon's Edge from Dagur's Berserkers and Ryker Grimborn's Dragon Hunters. Fishlegs then used air mail to stay in contact with Heather secretly.
The Dragon Hunters also used air mail with their captured terrible terrors. During one of their Dragon Fights, one of the hunters attempted to send a message to the Dragon Hunters' Arena to warn them of the Dragon Riders' approach. However, Heather was able to intercept it before it got there. The Dragon Hunters' Chieftain, Viggo Grimborn used it to send a message to Hiccup to discuss a truce between them.
- Various terrible terrors