All professional occupations demand a certain level of competence of their members. The aim of the thesis is to illuminate how professional knowledge is formed in a high-tech and risky environment with systems and tasks that are very unforgiving towards failures. The empirical basis is studies of four professional groups in the Swedish Air Force: flight technicians, fighter pilots, interceptor controllers, and air observers. These studies are assembled in a special report, supplementary to this thesis, entitled 'Four professional groups in the Swedish Air Force. Collection of studies 1985-1997, (Fyra yrkesgrupper i det svenska flygvapnet. Samlingsvolym 1985-I 997)'.

All in all about one thousand of officers have participated in the studies. The interplay between structural and cultural influences is put forward, together with the repercussions this has on the contents of work, work relations and professional identities. The result shows two pictures of the Swedish Air Force. One is of an organisation with considerable focus on training and development, and with a strong commitment from the employees to flying and flyingrelated tasks. The other is of an organisation where daily work involves considerable routine, repetition and monotony.

In conclusion, to successfully live up to the demands of being a professional in a state of readiness also has a price: the need to repeatedly perform without error in a high risk environment, always balancing effectiveness and flexibility with stability, perfectionism and foresight, also go together with tensions between different organisational levels and professionalgroups. These phenomena, which can be assembled under the concept 'professional trust' will certainly be more challenging within the Swedish Air Force extended future context, exemplified by joint operations, a network based defence and broader international co-operation.