Airdrop is a lootable entity, that is periodically randomly spawned in the world.
By default, an airdrop is dropped once every 3 days at noon, though the frequency can be changed in the Config. The airdrop always spawns at Y=255. The exact coordinates aredetermined b the number of people online.
If there is only 1 player online, a random position with a distance in the range 256-512 blocks is chosen. If more player are online, a random position with a distance from a point, whose X coordinate is the average of all player's X coordinate and Z coordinate is the average all player's Z coordinate, in the range 256-512 blocks is chosen.
Whenever an airdrop is spawned, a message saying "Airdrop has been dropped around X: Z:." is send to all players online. The coordinates in the message are offset by 32-128 blocks along both X and Z axis.
Airdrop can also be spawned by throwing the Flare item.
Initially the airdrop falls down with the speed of 0.0625 blocks per tick (about block pixel, when using 16x16 textures). Upon landing the airdrop starts emitting smoke particles for 1200 ticks (60 seconds), and loses the parachute. If the airdrops starts falling again after landing (because of destroyed ground, for example), it falls down with speed of 0.1911 blocks per tick.
The airdrop has lifespan of 48000 ticks (2 Minecraft days) when spawned. Upon opening the lifespan is reduced to no more than 6000 ticks (depends on the remaining life span before opening).