Proceeding On Assumption. Structural Validity in Aviation - Andrew T. Wahl

Proceeding on Assumption: Structural Validity in Aviation

Every accident investigation eventually finds it. The moment when everything was still legal, still within limits, still procedurally correct - and the structure that made safe execution possible had already failed.

Aviation has spent sixty years building frameworks to catch errors during execution. Threat and Error Management. The Swiss Cheese Model. Crew Resource Management. Each one is a genuine achievement. Each one assumes something it cannot guarantee: that the plan being executed is still valid, that the margin being relied on is still intact, that the person accountable still controls the conditions that will determine the outcome.

This book names that assumption. And gives crews a framework to evaluate it.

The Structural Validity Check asks three questions - continuously, across every phase of flight, from gate to gate:

Strategy: Does the current plan still correspond to the actual problem being faced - not the one assumed at the briefing?

State: Is the operation still inside a recoverable envelope, with margin that is not in doubt?

Authority: Does the person making decisions have both the information and the ability to act on them?

These are not checklist items. They are a discipline - one that operates upstream of every framework currently in use, catches what no alert will sound for, and gives crews standing to act before the doors start closing.

Built alongside SVC is LIFT - a gate-to-gate prioritization loop that keeps the framework operational across every flight phase. Legalities. Inflight Weather. Fuel. Terrain. Not a checklist but a continuous radial scan, anchored at the nose of the airplane, expanding outward, running from pushback to block-in.

Through five landmark case studies - Qantas 32, United Airlines 232, Reagan National January 29 2025, Southwest Airlines 554, and a simulator scenario built from a real crew's real failure - the book demonstrates what structural validity failure looks like before anyone makes an error, and what the framework gives crews to act on while options are still open.

Proceeding on Assumption is written by a retired Air Force Colonel and Operations Group Commander, National Guard Bureau Instructor Pilot of the Year, and current Boeing 737 line captain with more than 8,200 hours across three decades of military and commercial operations. It is not a theory. It is what thirty years of watching competent crews proceed past moments that should have stopped them - without a name for what was happening - finally produced.

The field has language for what goes wrong during execution.

This book gives it language for what goes wrong before.