NoCheatPlus, also known as NCP, is an anti-cheat system used by the Hypixel Server.
NoCheatPlus is a plugin that attempts to prevent cheat clients from exploiting weaknesses of Minecraft or its protocol, making your server safer from hackers. Checks cover a wide range of issues including flying and speeding, fighting hacks, fast block breaking and nukers, inventory hacks, chat spam and other types of malicious behaviour.
When a player is detected ascending into the air (or speeding drastically) at a high rate of speed, the player will be brought back to the place that they ascended from in the form of "lagging back." This all happens in less than a second or even milliseconds.
The result of lagging back would not result in a ban, but instead, it will only leave the player paralyzed for approximately one to two seconds after the effect. If the player flies or uses any other speed hack again after that, the same will happen, but the player would still not be banned, unless the action is recorded and sent to a Moderator.