Flying

Flying is the most versatile form of transportation and can only be used in Creative mode, although third-party mods can enable flying in Survival mode. Flying makes the Player move at around 10.8 meters/second (38.88 km/h), which is about 250% faster than the normal walking speed, being 4.3 meters/second. Flying decreases the Player's friction by a lot, making the player move as if they were on ice. If a player is flying in fluids they will not sink or slow down.

Flying is not limited by any processes such as food depletion, which limits sprinting. Flying mode can be toggled by double-tapping the "jump" key and can be activated at any altitude. The player can gain or lose altitude while flying by pressing the "jump" or "sneak" keys, respectively. Flying mode is automatically disabled if the Player lowers onto a surface while in the air. Flying increases the player's field of view by 10. A way to tell if you are flying or walking is to look at the Sun or Moon, which will zoom in or out during the mode change. Flying is useful in combat because the player can not only take its victim by surprise, but can also deal critical hits if moving downwards while attacking.

In Minecraft Pocket Edition, the player ascends or descends by sliding from the center button to the up or down button, respectively.

If the Player gets into a minecart or bed while flying, they will still be flying when they get out of the minecart or bed.

Players flying in the Void will only receive Void damage if they are below altitude -64, allowing them to fly a short distance beneath Void level.

Flying is usually not enabled on vanilla servers, so if the player is in Survival mode and is in the air for an abnormally long time, they will be kicked.

History
Flying was implemented in Beta 1.8pre1 along with sprinting, and was officially added in Beta 1.8, the Adventure Update.

Jeb tweeted about it, etc.

Until snapshot 12w17a the player would slow down when traveling in fluids, just like in survival.

While flying the jump button increases altitude, while the left SHIFT key lowers altitude. If rising high enough you apparently leave the atmosphere and can see both the sun and moon while the land is surrounded by stars.

Bugs

 * When flying near unusual level surfaces such as Redstone Repeaters, it is possible to sink 1 block into the ground.
 * The Player can activate flying mode and fly up or down while sleeping, although the player cannot move the field of view.

Trivia

 * It is possible to sprint while flying; sprinting and then activating flying gives a minimal speed boost.
 * If a player flies very close to, but not on the floor, he/she will make a large amount of stepping sounds when moving.
 * If the player switches from Creative mode to Survival mode ingame while flying by using mods (ex. Too Many Items), the player will continue to fly, but the second the player hits the ground, the player will be hurt or killed due to the accumulated fall damage.
 * If the player goes high enough while flying in Creative mode, the sun can be seen through the fog even if the player looks down; the player can also see the clouds at this time.