Seasonal variation of grounding rates among B-52H aircrew

Military commanders and physicians have long suspected that lost duty time attributable to illness increases during the winter months, the so-called "cold and flu season." For military aviation, there are remarkably few data in the literature to support or refute this idea. This study was undertaken to rectify that situation. The combined grounding rates of three operational B-52H Stratofortress squadrons were calculated and tracked for 28 consecutive months using FLYREC, a DOS-based grounding management database. A tally of the grounding diagnoses was also calculated. Results showed an overall grounding rate of 6.06%. The grounding rate for the winter months (December, January, and February) was 7.89% (95% confidence interval, 6.70-9.08), whereas the grounding rate for the summer months (June, July, and August) was 4.74% (95% confidence interval, 3.97-5.50). Respiratory illness of one type or another accounted for 70% of the total number of days grounded. In conclusion, grounding rates appear to vary by season of the year, with higher rates in winter than in summer. Communicable respiratory illness possibly accounts for this seasonal variability.