This map features a recreation of Simply Jetpacks which is an existing mod for Minecraft Java Edition but this map creation is only using command blocks, redstone and some custom textures to enable some of those features in-game. It's obviously much more limited than the mod but it is still really cool to see the power of command blocks.
How does it work?
Before you can use a jetpack you will need to craft it. The crafting works a little bit different than usual. Place a dropper (facing upwards) and then place the crafting ingredients in the dropper.
I highly recommend that you check out the video further down on this page as it explains everything in more detail.
Equip the jetpack in your hand to start flying. Just make sure you've got some coal in your inventory to power it. It will only work within a certain proximity of the command block machine.