Aircraft manufacturing involves an operation called sealing during which fuselage joints are sealed utilizing a sealant and smoothing tool, requiring motion of a worker's arms at heights below the elbow to overhead. The objective of this study was to assess the impact of shoulder exoskeletons on shoulder and torso muscle activation compared to no exoskeleton during simulated aircraft sealing tasks. Electromyographic signals from bilateral pairs of the anterior and medial deltoids, trapezius, latissimus dorsi, triceps, biceps, and erector spinae were collected from 16 aircraft workers as they performed simulated horizontal and vertical sealing tasks at heights ranging from chest level to above head level while wearing three different passive shoulder exoskeletons and a no-exoskeleton condition. Normalized electromyographic signals were assessed by two-way within-subjects ANOVAs and post-hoc tests. Exoskeletons consistently significantly reduced normalized EMG for the anterior deltoid and medial deltoid muscles at both horizontal sealing heights and during vertical sealing motions, with greater reduction in normalized EMG realized at higher vertical heights. While these laboratory results are encouraging, these exoskeletons must be evaluated in worksite studies to better assess their efficacy. Relevance to Industry: Passive exoskeletons are receiving increased interest as potential interventions to reduce muscular loading and work-related musculoskeletal disorders. The findings from this study on multiple passive shoulder exoskeletons highlights the impact on shoulder and torso muscles during simulated aircraft manufacturing sealing tasks. These results must be considered in context with other factors that may also impact effectiveness of passive exoskeletons including other task locations, comfort from wearing exoskeletons for extended periods, environmental conditions, hygiene, among other considerations.