Epic Games confirmed in a tweet that the Jetpack will be available tomorrow at 5am PT/8am ET. There will be no downtime as a part of the Jetpack release.
The Jetpack in Fortnite seems to be coming soon. The device was announced for Fortnite Battle Royale back in February 2018, but it was delayed out of its initial launch period and then fell off the radar completely.
According to a data mine from @FNBRleaks on Twitter, the Jetpack will finally be arriving before Week 5 of Fortnite Season 4, which is set to launch on Tuesday, May 29.
As part of the Fortnite Week 5 Challenges slate, players that own the Battle Pass will be tasked to 'Use a Jetpack' in return for five Bronze Stars.
Another interesting leak through the data mine is a new Limited Time Mode called 'Close Encounters'. This mode is described as "Close quarters combat with Shotguns & Jetpacks! If you find a jetpack, double-tap the jump button to take off. Keep the button held down to apply thrust. Make sure to land before it runs out of fuel!"
Based on this discovery, it seems likely that the Jetpacks will be added into Fortnite Battle Royale before the challenge surrounding the tool goes live in Week 5.