Instructions: 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.
Input:   The planning system is critical to the viability and operation of GA aerodromes . With many cities lacking scheduled air transport services between them , and with GA access to commercial airports becoming increasingly difficult and expensive , a viable network of aerodromes supporting GA air transport operations is regarded as an important national issue . However , there is no unified national planning policy specific to GA aerodromes , and planning decisions relating to these are based on local issues that are not required to consider the national impact . Because aircraft are excluded from noise control legislation , the only recourse for people affected by aircraft noise is through the planning process , and this issue is the principal factor on which the majority of planning decisions relating to GA land use are made . GA is a specialist subject often unfamiliar to Local Planning Authorities , and most planning decisions relating to GA either refuse permission , or grant it with restrictive conditions . Little Gransden is just one example of a GA airfield required to comply with planning restrictions on the number of movements permitted , thereby inhibiting further development . Such restrictions , if poorly conceived , can make GA operations unviable or even unsafe . fill in the blank  : The planning system is __________________ to the viability and operation of GA aerodromes . 
Output:
 critical 