Q: In this task, you will be given a passage to read. A fill in the blank question will be given to you.  Your answer should fit the blank appropriately.
There are an estimated 27 @,@ 000 civil aircraft registered in the UK , 96 per cent of which are engaged in GA activities . In 2005 the GA fleet comprised 9 @,@ 000 fixed @-@ wing aircraft , 4 @,@ 100 microlights , 1 @,@ 300 helicopters , 1 @,@ 800 airships / balloons , 2 @,@ 500 gliders and some 7 @,@ 000 hang gliders . Estimates put the number of foreign @-@ registered GA aircraft based in the UK at 900 . The number of pilots licensed by the CAA to fly powered aircraft in 2005 was 47 @,@ 000 , of whom 28 @,@ 000 held a Private Pilot Licence . The remainder held professional pilot licences , either a Commercial Pilot Licence or an Airline Transport Pilot Licence , although not all of these would be engaged in GA activities . In addition , there are 10 @,@ 000 active glider pilots , and estimates put the membership of aviation @-@ related sport and recreational associations at 36 @,@ 000 . The number of aerodromes that support GA in the UK is difficult to establish with certainty . Pooleys 2008 United Kingdom Flight Guide lists 355 , and the Airplan Flight Equipment UK VFR Flight Guide 2008 lists nearly 500 . Lockyears Farm ' Strips ' and Private Airfields Flight Guide lists more than 300 landing sites . The GASAR study estimates 1 @,@ 100 formal flying sites in England alone , a figure which includes 400 sites known to planning authorities but not included in flight guides . It estimates another 759 informal sites known only to land owners , customs , and members of the enthusiast group Air @-@ Britain .The sector was estimated to employ nearly 12 @,@ 000 people and directly contribute £ 1 @.@ 4 billion to the UK economy in 2005 , making it roughly seven per cent of the size of the CAT industry . Nearly half of the economic contribution was generated by business aviation . fill in the blank  :There are an estimated 27 @,@ 000 civil __________________ registered in the UK , 96 per cent of which are engaged in GA activities . 
A:
 aircraft 