 Controlled 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 untenable " 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 VFR access to airspace , resulting in high numbers of GA flights operating close to the borders of controlled airspace who could not get formal receipt of an air traffic service . Coupled with pilot navigation errors , hundreds of airspace infringements have been recorded every year . 
 Controlled airspace <a href='drop_aux' title='1'><mark>is</mark></a>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 untenable " by commercial operators . However this position <a href='been_done' title='2'><mark>has</mark></a> resulted in extensive Class A controlled airspace with complex boundaries , including some running down to the ground , prohibiting VFR access to airspace , resulting in high numbers of GA flights operating close to the borders of controlled airspace <a href='null_relcl' title='3'><mark>who</mark></a>could not get formal receipt of an air traffic service . Coupled with pilot navigation errors , hundreds of airspace infringements <a href='been_done' title='4'><mark>have</mark></a> been recorded every year . 
Controlled airspace essential for the provision of a known air traffic environment necessary for da safe operation of CAT . A CAA review found that " mixing [ commercial ] operations with other users is considered undesirable , even untenable " by commercial operators . However this position done resulted in extensive Class A controlled airspace with complex boundaries , including sum runnin down to the ground , prohibiting VFR access to airspace , resulting in high numbers of GA flights operating close to tdaborders of controlled airspace could not get formal receipt of an air traffic service . Coupled with pilot navigation errors , hundreds of airspace infringements done been recorded every year .