Abstract

Critical ground time in organ, tissue, and team transport missions of the Brazilian Air Force exhibits substantial variability, creating a gap between deterministic fatigue-management assumptions and observed aeromedical operations. This study consolidates the dataset to mission level to avoid pseudoreplication from multiple-organ records. The analytical dataset comprised 583 mission-level observations derived from 712 organ records collected from January 2023 to May 2025 after mission-key reconciliation and consolidation. Rounded five-minute ground-time observations were analyzed with grouped-likelihood duration models, comparing Poisson, Negative Binomial, Gamma, lognormal, Weibull, and log-logistic alternatives. Refitted parametric bootstrap intervals and a chronological 2025 holdout were used to quantify uncertainty and temporal calibration. The mission-level median critical ground time was 80 min for unaccompanied transport, 245 min for simple procurement, and 275 min for multiple procurement. The corresponding fitted P95 benchmarks were approximately 155, 380, and 375 min, respectively, with later-mission exceedance rates close to or below the nominal 5% level in the chronological validation. These results support probabilistic planning benchmarks while clarifying that P95 is a risk-based planning percentile, not a guarantee of mission duration or safety.

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