Vertibird signal grenade

The vertibird signal grenade is a weapon in Fallout 4.

Characteristics
Soon after throwing a vertibird signal grenade, a vertibird will appear on the horizon and track towards the Sole Survivor and land in the vicinity of the marked location, albeit not instantaneously. The player character can then board the aircraft to take control of its side-mounted minigun. Opening the Pip-Boy map and selecting a location to fast travel to will cause the vertibird to lift off and start flying to the selected location. When the vertibird has landed, the player character may exit or use the Pip-Boy map to select a different destination. Alternatively, the player character can change the destination mid-flight using the Pip-Boy map.

The grenade produces a vertical plume of orange smoke. The vertibird signal grenade can only summon a vertibird when used outside. They can be used initally only when the player character is a member of the Brotherhood of Steel. They may be used by non-Brotherhood members of the Minutemen or the Railroad only upon completion of their respective main questlines. Prior to the completing the main questline, former members of the Brotherhood can use any grenades still in their possession to summon vertibirds, but the vertibirds and occupants will be hostile, and it will not be possible to use the vertibird for fast travel.

If the Sole Survivor completes the Railroad's main questline, after a few days Drummer Boy in the Railroad HQ will say that the vertibird is ready for use, giving the Sole Survivor three signal grenades. He then informs the player character that more can be purchased from Tinker Tom. Similarly, grenades can be purchased from Ronnie Shaw if the Brotherhood are (optionally) destroyed as part of the Minutemen ending to the main questline.

Unlike normal vertibirds and their crew, the summoned vertibird and its pilot are immune to all forms of damage, and cannot be targeted in VATS or with a Recon scope. However the player character can be harmed and killed while in the vertibird.

Variants

 * The Minutemen have two similar support items: flares and smoke grenades. The flare will signal for troops and the smoke grenades direct a strike from nearby artillery.
 * The Institute has synth relay grenades to spawn synths.

Locations

 * Eight are given by Elder Maxson as a reward for completing the quest Show No Mercy.
 * Sold by Proctor Teagan aboard the Prydwen after completing Show No Mercy.
 * Three are given by Drummer Boy upon completion of The Nuclear Option for the Railroad.
 * Sold by Tinker Tom at the Railroad HQ after completing The Nuclear Option for the Railroad.
 * Six are given by Preston Garvey after completing The Nuclear Option for the Minutemen, and upon destroying the Prydwen.
 * Sold by Ronnie Shaw after completing The Nuclear Option for the Minutemen, and destroying the Prydwen.