[en] The European Council directive 96/29/Euratom of 13 May 1996 emphasizes the introduction of two categories for occupational exposure. Category A includes the employees for whom the annual effective dose is likely to exceed 6 mSv. Suggesting an average flight time between 600 and 1000 hours per year for aircrew, the typical annual dose lies between 4 and 8 mSv with a maximum value of 15 mSv for Concorde flights. This requires the surveillance of aircrew members and thus the development of proper measurement devices. Because of the similar radiation environment, high altitude mountains seem to be an ideal choice to test and to improve recently developed measurement systems. Bonner Sphere Spectrometers (BSS) with a ⁶LiI(Eu) scintillation counter and thermoluminescent dosemeters (TLDs), respectively, were used to determine the neutron energy spectrum as well as the absorbed dose and the average linear energy transfer (LET) in a complex mixed radiation field on top of Mt. Sonnblick (3105 m). The neutron component makes up 35 to 60% of the biologically relevant dose at high altitudes, depending on the geomagnetic latitude. The average LET of the mixed radiation field was determined using the high temperature ratio (HTR)-method. Paired TLD-600 and TLD-700 dosemeters as well as an extended range Sievert counter were employed for determination of the neutron dose equivalent. Furthermore, a LET spectrum was recorded on Mt. Kitzsteinhorn (3029 m) using the laboratory-manufactured tissue equivalent proportional counter (TEPC)-system PART. All detectors were calibrated with standard radiation sources and in the CERN EC neutron reference field. The measurements performed with the passive BSS as well as the Sievert counters show that there exists a neutron component with energies up to 100 MeV (and probably more) at such altitudes. The total dose equivalent rate measured on top of Mt. Sonnblick was 200 nSv.h^-1 compared to an absorbed dose rate of 120 nGy.h^-1. The neutron dose equivalent rate was 120 nSv.h^-1, i.e. about 50% of the total dose equivalent rate. The examinations show that thermoluminescent dosemeters in combination with the HTR-method are perfectly suitable for the determination of absorbed dose, neutron dose equivalent and total dose equivalent. Based on this method a monitoring system for the radiation exposure in aircraft is planned. (author)