With over 5000 flights per day on average in the UK alone, and this number ever increasing, safety is an ever growing concern in the world of aviation. A key safety mechanim used by these aircraft is Automatic Dependant Surveillance-Broadcast. Known better as ADS-B, this is the primary technology used for flight tracking apps, showing you where all the planes in the sky are. However, the nature of ADS-B's design from the late 1990s is that it is entirely unauthenticated and unencrypted. While this was not a problem at the time, as radio equipment was expensive and generally inaccessible. Since then, with the rise of affordable and powerful radio technologies such as SDRs, this risk is greater than ever. This talk will discuss the intial design of ADS-B and what it achieved, how it has grown and most importantly, the different security issues facing it. These inlcude considerations such as eavesdropping, message deletion and modification, and injecting new aircraft. The impact of these attacks will be discussed, as well as looking to the future and seeing what is being done to combat these threats.