2 An aircraft deviation of 300 feet or more from its assigned level

3 The Weighted SSE index is a single figure calculated by giving a weighted value to our 4 event scores ( SSE 1-4 ). These values are combined in the index to provide the measure of safety performance used within the company to track our overall safety progress over time . It distinguishes between those events that are attributed wholly or partly to NATS , and those that are not ( although both are addressed in our safety activities ). The SSE scheme categorises safety events based upon severity ( 1-4 ) and separation distance ( a-d ), where 1a is the most severe and 4d the least severe .

4 An Airprox is a situation in which , in the opinion of a pilot or controller , the distance between aircraft as well as their relative positions and speeds have been such that the safety of the aircraft involved was or may have been compromised . The severity of these incidents is assessed periodically by the UK Airprox Board , an independent body , in the interests of enhancing flight safety .

Our ambition is to accelerate through £ 1bn of sustainable revenue by 2015 and this year we reorganised our economically regulated and non-regulated businesses into six service lines . These reflect our core competencies and our routes to market and provide greater clarity to our customers of the capabilities offered under the NATS brand .

Our main priorities for the foreseeable future however , and the mainstays of the business , will remain Airspace and Airports where we believe there are plenty of opportunities to create customer value . The performance of the air transport network ( which is illustrated below ) relies on what happens from the cruise , on the ground and then back to the cruise and the complex interactions at each stage of flight between airlines , airport operators and NATS . We believe we are well placed to bring all parties together to improve the efficiency of the network and this will shape our strategy beyond 2015 .

Safety

Our first priority remains the safety of aircraft and the travelling public . We have an international reputation for our approach to safety management , our well established safety culture and our excellent safety record .

Our safety improvements focus on tackling operational risks and subsequent sources of safety incidents , including working with others in our industry to do so . The most significant operational risks are : infringements of controlled airspace , level busts 2 and human performance .

During the year we have reduced the Weighted Safety Significant Event ( SSE ) 3 index by a further 7 % when considering all events . For events that are attributable partly or wholly to NATS the reduction is 35 %. This is an excellent achievement and is a further testament to the work we have done to reduce our contribution to safety risk in aviation . Over the first two years of this control period we have

reduced the Weighted SSE index by a cumulative 26 % for all events and 36 % for events attributable to NATS .

For the fifth successive financial year we achieved our target of no category A or B Airprox 4 attributable to NATS and our strategic safety target to March 2015 is to maintain this record along with a further 10 % reduction in our Weighted SSE index .