Firecracker Freefall is a Rare Fortnite Contrail from the Ka-Bang! set. Firecracker Freefall was first added to the game in Fortnite Chapter 2 Season 7.
This cosmetic can be unlocked by completing a challenge in the Cosmic Summer Challenges event. Full list of challenges can be found here: All Cosmic Summer Challenges and Rewards.
Firecracker Freefall is part of the Ka-Bang! set! You can find all of the items that belong to it below.