In the early 1990s, two Boeing 737s fall out of clear skies moments before landing. One in Colorado Springs. One outside Pittsburgh. In both cases, the crews are experienced professionals flying perfectly maintained aircraft. The engines are running normally at impact. The weather in Pittsburgh isn't even a factor. And the investigators who comb through both crash sites — the best aviation safety analysts in the world — find almost nothing. What follows is the longest crash investigation in aviation history: a decade-long hunt through wreckage, laboratory tests, and dead ends that will demand a third aircraft, one surviving pilot, and one extraordinary experiment before the truth finally gives itself up. One hundred and fifty-seven people died before anyone understood why.

Sources:

1. Mayday: Air Disaster, Season 4, Episode 5, "Hidden Danger"
2. NTSB Aircraft Accident Report AAR-01/01 — United Airlines Flight 585, Amended Final Report, March 27, 2001
3. NTSB Aircraft Accident Report AAR-99/01 — USAir Flight 427
4. NTSB Human Performance Group Chairman's Factual Report — Eastwind Airlines Flight 517 (DCA96IA061)
5. FAA Airworthiness Directive AD 94-01-07
6. FAA Airworthiness Directive AD 99-11-05
7. FAA Airworthiness Directive AD 2002-20-07
8. FAA 737 Flight Controls Engineering Test and Evaluation Board (ETEB) Findings and Recommendations Summary
9. Auralis Skies, "The Day an Airplane Took Control — and No One Survived"
10. The Seattle Times, "Safety at Issue: The 737" investigative series
11. Denver Westword, "Flight Diversions"
12. WTAE Pittsburgh, "Flight 427: Pennsylvania's Deadliest Plane Crash, 30 Years Later"
13. Planesafe.org — Gail Dunham, "Safety – 737 United 585 – Postscript," June 7, 2001
14. AeroTime, "Revisiting the Boeing 737 Rudder Issues of the '90s"
15. Aviation Stack Exchange — Boeing 737 rudder servo valve vulnerability discussion
16. Simple Flying — aircraft component temperature changes in flight
17. NTSB Press Release, September 26, 2024 — urgent safety recommendations on Boeing 737 rudder system
18. Aviation Safety Network — United Airlines Flight 585 accident description
19. Aviation Safety Network — USAir Flight 427 accident description
20. Wikipedia — United Airlines Flight 585
21. Wikipedia — USAir Flight 427
22. Wikipedia — Boeing 737 rudder issues
23. Everything Explained Today — United Airlines Flight 585 pilot biographical details
24. Justapedia — Captain Harold Green
25. Virginia Tech Libraries — USAir Flight 427 passenger list
26. Historical Marker Database (HMDB) — Widefield Community Park memorial marker
27. Find A Grave — Captain Peter Germano
28. Find A Grave — First Officer Charles B. "Chuck" Emmett III

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Credits: Final Boarding Call is hosted by Alice Stern and Zach Stemas, researched and written by Alice Stern, produced and edited by Alice Stern and Zach Stemas.