Letters of agreement set out the high-level policy for cooperation between states under contingency conditions and can cover operational as well as technical support.
Letters of agreement provide ways of establishing mutual support under contingency. They enable planning well before an incident takes place. Testing and exercises can be used to determine whether or not states can implement the joint approaches described in letters of agreement. For more details on the legal issues involved see the article Legal Aspects of Contingency.
Air navigation service providers (ANSPs) often draft collaborative agreements with neighbouring States so that they will assume responsibility for some of their workload under contingencies. This can be flexible and cost-effective. In addition to the operational load sharing, it is also possible to draft technical letters of agreement. Several European states operate the same core technical systems, which have been tailored for their particular operational needs. This may be particularly appropriate in Functional Airspace Block (FAB) arrangements (and later within the context of the SESAR (Single European Sky Air Traffic Management Research) - deployment). In this approach, international letters of agreement are extended beyond immediate operational requirements to provide wider systems support. Several ANSPs have begun to develop agreements for the joint procurement of common infrastructures; these agreements provide a template for the exchange of technical support under contingency. For instance, it may be feasible for systems engineers from one ANSP to be sent to help those of a ‘failing’ unit in another country.
There are potential risks associated with the arrangements specified in letters of agreement - for example, in ensuring that air traffic controllers (ATCOs) and engineers in neighbouring states meet licensing and training requirements. Further issues relate to the legal status, competency and certification of individuals from another country. There are few examples of engineering staff being deployed to help an ANSP from another state, in time to respond effectively to a contingency. Hence this approach remains largely unproven even if the situation may change with the increasing use of common infrastructure components in future ATM systems.