Until data link communication comes into widespread use, air traffic control will continue to depend heavily upon voice communications, which are affected by various factors. Any breakdown in communication between pilot and ATCO can result in a hazardous situation, especially in controlled airspace. Alternative means of communication do currently exist but they are still very limited in their capability to substitute for RTF as usually employed.
The pilot failing to fly the required vertical profile which may lead to a level bust, or not following the required horizontal profile:
Either situation may cause the aircraft to make an unauthorised entry of designated airspace (airspace infringement) which may leading to disruption of air traffic causing risk to other airspace users and increased workload for pilots and controllers, or may put the infringing aircraft at risk from ground hazards such as artillery firing;
Either situation can lead to loss of separation from other aircraft, or airborne objects (Ballons or parachutists for example) which may result in collision.
Level bust may also lead to collision with an obstacle or the ground (CFIT);
Injury, especially to cabin crew or passengers, may be occasioned by sudden manoeuvres to avoid collision with other aircraft or the ground, or as a result of a wake vortex turbulence encounter;
The pilot changing to an incorrect frequency or not implementing a frequency change, leading to:
Recognise and understand respective pilot and ATCO working environments and constraints.
Listen to other communications on the frequency to build situational awareness, avoid talking over transmissions by other users, and be alert to potential call sign confusion.
Promotion of, and training in, Crew Resource Management in order to ensure that SOPs are applied in best possible way to ensure:
The flight clearance is understood. This includes checking to ensure that both pilots agree and understand the flight clearance (cross-checking is a role overseen by the monitoring pilot/crew member);
The aircraft follows the flight clearance and does not unintentionally deviate from it. This includes checking the settings made to technical equipment and monitoring the performance of that equipment and the aircraft in order to detect any error or malfunction.
For further information refer to the EUROCONTROL "AllClear" Toolkit. The AllClear toolkit provides numerous downloadable training products, videos, and computer based training examples for pilots and controllers.