British Airways has carried out radiation monitoring in Concorde for more than 20 years and has used a heuristic model based on data quoted by the National Aeronautics and Space Administration (NASA) to model radiation exposure in all longhaul fleets. From these data it has been calculated that no flight deck crew would exceed the control level of 6 mSv/y currently under consideration by regulatory authorities, which is three tenths of the occupational dose limit of 20 mSv/y recommended by the International Commission on Radiological Protection (ICRP). The model suggested that less than 4% of cabin crew based in Tokyo flying only between London and Japan could reach or exceed the 6 mSv/y level, based on a predicted effective dose rate of 7 microSv/h. To validate this calculation a sampling measurement programme was carried out on nine round trips flown by a Boeing 747-400 between London and Tokyo. The radiation field was measured with dosimeters used for routine personal monitoring (thermoluminescence dosimeters (TLDs) and polyallydiglycol carbonate neutron dosimeters). The limitations of the methodology are acknowledged, but the results indicate that the effective dose rate was 6 microSv/h which is consistent with the predicted effective dose rate of 7 microSv/h. This result, which is in accordance with other reported studies indicates that it is unlikely that any of the cabin crew based in Tokyo exceeded the 6 mSv/y level. In accordance with "as low as reasonably achievable" principles British Airways will continue to monitor flying crew routes and hours flown to ensure compliance.