Notes on verification

Confirmed by multiple independent authoritative sources including Air Force Historical Support Division, Guinness World Records, and Smithsonian, all consistently identifying Selfridge as the first fatality in a powered, heavier-than-air aircraft crash (1908, Wright Military Flyer, Fort Myer). [cascade flags: wikipedia_dropped_other_sources_exist | tier=silver indep_score=1.0 clusters=2 claim_tier=notable | framework convergence=partial (upstreams: Guinness World Records, Air Force Historical Support Division) — publishers independent, evidence may not be | kind=interpretive eligibility=high (extractor: interpretive/medium)]