The way that CRII is modulated and distributed inside the atmosphere affects human exposure to radiation, suggesting that air crew members and frequent flyers of commercial flights should be treated in a specific way and extra safety measures and necessary regulations should be applied during their flights. Other than ones referring to the general public, specific regulations and safety measures do not yet exist for frequent flyers. However, the European Commission, as well as other entities such as the International Commission on Radiation Units and Measurements (ICRU) and the International Committee on Radiological Protection (ICRP), have adopted a series of recommendations and frameworks regarding the determination of the occupational exposure of aviation crews to cosmic radiation, as well as the most efficient measures and counteractions to ensure radiation protection [17; 18; 19]. For this reason, several studies on the problem have been performed [20; 21; 22; 23; 24; 25; 26; 27], while various models and tools have also been developed by the scientific community in cooperation with the aviation industry. Some of these well-known models are the following: SIEVERT [28], AVIDOS [29], NAIRAS [30], CARI [31], CALVADOS [32] SPENVIS [33], CRAC:DOSE [23] and PLANETOCOSMICS [10]. Furthermore, ionization also affects the avionic electronic systems during a flight, with single event effects (SEEs) being a main factor in this [34; 35]. To expand, a single secondary high-energy atmospheric neutron can collide with a nucleus of the semiconductor, causing an ionization charge that can affect a semiconductor device. The most common effects of SEEs are soft errors, firm errors and hard errors that decrease the performance and the availability of electronic systems. Furthermore, radiation can also affect optical components (i.e., LEDs, lasers and optical fibers), by changing their optical properties and causing displacement damage. Usually, the electronic and optoelectronic devices anneal after the irradiation has stopped but, in some cases, radiation can cause permanent damage [36; 37; 38]. Therefore, it is crucial to estimate the ionization and radiation levels during a flight in order to be able to maintain reliability standards. In this work, the CRII was calculated for three different flight levels (FLs): FL310 (9.45 km a.s.l. or 31,000 ft), FL350 (10.67 km a.s.l. or 35,000 ft) and FL390 (11.89 km a.s.l. or 39,000 ft). The model used for the aforementioned calculations was the CRAC:CRII model in its extended version [12; 13]. The CRII for these typical FLs is depicted in ionization maps (Figure 1), showing the distribution of CRII globally for specific phases of solar cycles 23 and 24 (i.e., solar maxima and minima). More to that, time profiles of the monthly distribution of CRII for selected magnetic cut-off rigidities for the same FLs during solar cycles 23 and 24 will be presented. In addition, a similar study concerning the radiation assessment of occupational exposure to cosmic rays, specifically the estimation of the ambient equivalent dose rate for the typical FLs, was performed. For these calculations, the software application Dynamic Atmospheric Shower Tracking Interactive Model Application (DYASTIMA) [39; 40] of the Athens Cosmic Ray Group was used. Finally, regarding the investigation in this work, a combined study was performed and a correlation between these two physical parameters is shown.