ICRP Publication 60 recommended that the radiation exposure due to the cosmic component at high altitudes be considered when appropriate as part of occupational exposure to the radiation. The recommendation was incorporated to the Czech regulation in 1997, and the studies on how to perform individual dosimetry of Czech companies aircraft crew started immediately. The individual monitoring values were calculated using the Transport code CARI. The results obtained since the beginning have been recalculated, now with the version 6. The information on the flight schedules and the participation of aircraft crew in the flight were received from the air company. Routine individual dosimetry had started in 1998. Main results for the period 1998-2003 are as follows: both relative frequencies, as well as, average annual effective doses vary with the company and with the year, without any evident general tendency; the average annual values of E were between 1.5 and 2 mSv; and collective effective dose increased regularly, from approximately 1.5 manSv to >2.2 manSv. More detailed analysis is presented, including the verification of the procedure by a series of onboard experimental measurements.

Department of Radiation Dosimetry Nuclear Physics Institute Czech Academy of Sciences Prague Na Truhlarce 39 64 CZ 18086 Praha 8 Czech Republic