Stratospheric aerosol delivery requires 20 km aircraft with extreme wingspans beyond 12 km commercial ceilings

Engineering assessments show conventional jets top out near 12 km while target injection demands sustained flight at 20 km where thinner air requires wingspans exceeding 100 m on stubby fuselages. Iris Aero's water-strider configuration illustrates the redesign: lift-to-drag ratios must compensate for density drops of roughly 90 percent. University of Chicago precursor studies confirm sulfuric acid stickiness necessitates lighter SO2 or H2S carriers, yet each adds payload mass and corrosion constraints not captured in climate models. Deployment bottlenecks compound when scaling from single flights to annual megatonne injections. Annual mass requirements exceed 5 Tg S, demanding fleets of dozens of aircraft operating continuously from dispersed bases. Governance gaps widen as engineering blueprints become public; modeling papers alone do not equate to flight hardware, yet detailed airframe specifications lower barriers for state or private actors to replicate systems unilaterally. Operational reality diverges from volcanic analogs. Mount Pinatubo injected 20 Tg SO2 once; sustained geoengineering requires equivalent yearly output with precise particle size control to avoid coagulation losses. This shifts research from atmospheric simulations toward certification, maintenance, and refueling logistics at altitude, none of which appear in current IPCC scenarios. Next milestones include subscale stratospheric test flights and precursor chemistry flight validation within five years.