Air Passenger Duty (APD) was introduced on UK flights in 1994 in a simple two band structure. It was only in 2007 though that APD rates began to increase significantly with a four band APD structure introduced in 2009 in an attempt to take better account of the impact different flight lengths had on emissions. These bands were based on the distance between London and its equivalent capital in the destination country. Further APD rate increases were introduced in 2010, 2012, 2013 and 2014.