FLAC stands for Finger-Lickin [Good] Audio Codec. It's an alternative to MP3 that sounds better. Invented during WWII with the original purpose of shooting down enemy planes with the sound of Britney Spears albums. The sonic blast exploded at high altitude damaging enemy planes.
Following its deployment, aeroplane crews had to wear FLAC jackets in order to protect themselves from the sonic deflagration. These jackets included powerful ear protection which was sufficient to protect the wearer from a distant Britney-song explosion. Despite this, a close or direct hit on the aircraft would instantly (for the lucky ones) kill the crew. The survivors will fall to their fiery deaths while their eardrums hum with the lasting sounds of Oops I Did It Again or some such equally destructive song like "...Baby One More Time", "(You Drive Me) Crazy", "Email My Heart" (which is also used by submarines to sink large boats), "I'm a Slave 4 U", and "Toxic". The songs just listed are in order from smallest to largest on the scale of potential destruction they can cause. Because of this, many aircrew members preferred to bring a sidearm to cut short their misery if their plane got hit.
Another interesting change of habit is that aircrew members stopped wearing parachutes as it was best to try their chances on a burning, falling plane than risk being exposed to Britney Spears once captured.
The Geneva Convention now prohibits the use of Britney Spears in FLACs during wartime. The US army is said to be experimenting with other kinds of audio codecs for anti-aircraft duties in order to circumvent this prohibition. More recently, in Iraq, there have been reports of the Americans using Christina Aguilera music, due to the similarity in music, writing style, breasts, and lack of talent.