 <unk> airspace is essential for the provision of a known air traffic environment necessary for the safe operation of CAT . A CAA review found that " mixing [ commercial ] operations with other users is considered undesirable , even <unk> " by commercial operators . However this position has resulted in extensive Class A controlled airspace with complex boundaries , including some running down to the ground , prohibiting <unk> access to airspace , resulting in high numbers of GA flights operating close to the borders of controlled airspace who could not get formal <unk> of an air traffic service . Coupled with pilot navigation errors , hundreds of airspace <unk> have been recorded every year . 
