The Cost of Not Dropping In: Aircraft Redesign vs. Specification Reform

Draft analysis — pre-publication. Do not distribute.

1. The Central Argument

If SAF's specification barriers were relaxed where technically justified, much of the price premium could be eliminated using existing aircraft, engines, and infrastructure — with zero capital investment in the fleet. The alternative approaches (hydrogen, electric, new engines) require trillion-dollar investments, decades of development, and entirely new infrastructure.

Key question: Is it more cost-effective to relax fuel specifications by a few percent, or to redesign the global aircraft fleet from scratch?

2. Historical Aircraft Development Costs

Program	Type	Dev. Cost	Timeline	Notes
Boeing 787 Dreamliner	New widebody	$32B (est. $50B total)	8+ years (2004→2011)	Composite fuselage, new engines (GEnx/Trent 1000); massive cost overruns
Airbus A350 XWB	New widebody	$12–15B	9 years (2006→2015)	Carbon composite; leveraged A380 tech; lower overruns than 787
Boeing 777X	Derivative	~$15B	10+ years (2013→2026?)	Folding wingtips, GE9X engines; still not certified as of early 2026
Airbus A320neo	Re-engine	~$1.5B	4 years (2010→2014)	New engines (LEAP/PW1100G) on existing airframe; lowest-risk approach
Boeing 737 MAX	Re-engine	~$3B	5 years (2011→2017)	LEAP-1B engines; MCAS issues added billions in remediation

Sources: Seattle Times (2011); Simple Flying (2025); Boeing/Airbus disclosures; Aviation Stack Exchange compilation.

3. Engine Development Costs

Engine	Developer	Dev. Cost	Timeline	Notes
CFM LEAP	GE/Safran	~$2.5B	9 years (2005→2014 cert)	Powers 737 MAX & A320neo; ceramic matrix composites, 3D woven fan blades
Pratt & Whitney PW1100G (GTF)	P&W	~$10B	~25 years concept→cert	Geared turbofan; revolutionary architecture; persistent durability issues
GE9X	GE Aerospace	~$3B	8 years (2014→2022 cert)	World's largest fan; ceramic matrix composites; powers 777X
Rolls-Royce UltraFan	Rolls-Royce	~$2–3B (est.)	In development	Demonstrator tested 2023; production TBD
CFM RISE (Open Fan)	GE/Safran	TBD ($5B+ est.)	2025→2035+ target	Open fan architecture; 20% fuel reduction target; requires new nacelle/airframe

Sources: CFM International; GE Aerospace; P&W disclosures; industry analyst estimates. Engine development $1.5–3B typical; $5B+ for revolutionary architectures.

4. Non-Drop-In Alternatives: Total System Cost

4a. Hydrogen Aviation

Component	Cost Estimate	Timeline	Source
Airbus ZEROe aircraft development	€15B ($16B) over 10 years	Originally 2035, now 2040–2045	Transport & Environment (2023); Airbus (Feb 2025)
Airbus spent to date (as of 2025)	$1.7B (stalled)	Program delayed 5–10 years	Flying Magazine (Apr 2025)
Airport hydrogen infrastructure (global)	$700B–$1.7T by 2050	25+ years	WEF/McKinsey (Apr 2023)
Hydrogen production + distribution	€299B ($320B) for intra-EU only	Through 2050	TUHH/Steer for T&E (Apr 2023)
Hydrogen liquefaction (per airport)	$50–200M per major airport	5–10 years per installation	McKinsey "Target True Zero" (2023)
New certification framework	Unknown — no precedent for H₂ commercial aviation	Years of rulemaking	FAA/EASA

Airbus ZEROe: Delayed and Downsized. In Feb 2025, Airbus officially pushed ZEROe from 2035 to 2040–2045, acknowledging the "hydrogen economy" is 5–10 years behind 2020 assumptions. The initial target was a 100-seat turboprop — not a replacement for single-aisle or widebody aircraft. Even if successful, hydrogen aircraft would address less than 15% of global aviation CO₂ (short-haul intra-regional routes only). Long-haul — where most emissions occur — remains SAF-dependent regardless.

4b. Battery-Electric Aviation

Parameter	Current State	Required for Commercial Aviation
Battery energy density	~250–300 Wh/kg (Li-ion)	>800 Wh/kg for 500+ nm range
Viable aircraft size	9–19 passengers, <150 nm	150+ passengers, 500+ nm
eVTOL certification (Joby, Archer)	Approaching Part 21 cert in 2025–2026	Urban air taxi, not airline replacement
Infrastructure (vertiports)	$5–50M per vertiport	N/A for airline-scale operations
% of global aviation addressable	<2% (ultra-short haul only)	Physics-limited by battery weight

Physics constraint: Jet fuel has ~12,000 Wh/kg energy density. Batteries at 300 Wh/kg are 40× worse. Even at a theoretical 1,000 Wh/kg (beyond any known chemistry), a battery-powered 737-class aircraft is not feasible for ranges >500 nm. Electric aviation will serve urban air mobility and very short hops — it cannot replace the existing fleet.

4c. New Clean-Sheet Aircraft (Conventional Fuel)

Even designing a new conventional aircraft optimized for SAF/alternative fuels requires:

$15–30B development cost (based on 787/A350 precedent)
5–9 years for FAA/EASA certification
10–15 years to achieve meaningful fleet penetration (airlines don't replace aircraft overnight)
Still needs fuel — just optimized differently

5. The SAF Specification Reform Alternative

Reform	Cost	Timeline	Impact
Relax viscosity spec (−20°C limit)	~$0 (testing only: ~$2M)	1–3 years (ASTM ballot)	Reduces hydrocracking severity → higher yield → lower cost
Remove/relax phosphorus 2 ppm	~$0 (if technically justified)	1–3 years (data + ballot)	Reduces pretreatment cost for lipid feedstocks
Raise blend limits (50→100%)	~$50M (additional testing)	3–5 years	Doubles addressable market, eliminates logistics burden
Streamline D4054 qualification	~$0 (process reform)	1–2 years	Reduces barrier from 5–7yr/$10M to 2–3yr/$2M
Policy: Include jet in CAR	$0 (regulatory)	1–2 years	+$0.30/gal parity with RD in California
Policy: Equalize RIN EV (1.6→1.7)	$0 (regulatory)	1–2 years	+$0.09/gal parity with RD

6. Comparison: Total System Cost by Pathway

7. Key Takeaways

The orders-of-magnitude argument:

SAF spec reform: ~$50M, 1–3 years, uses the entire existing fleet of 25,000+ commercial aircraft
Hydrogen aviation (global): $700B–$1.7T, through 2050, addresses <15% of emissions, requires new aircraft + new infrastructure at every airport
That's a 10,000–30,000× difference in cost for a solution that's available now vs. one that's 20+ years away and limited in scope

The non-drop-in alternatives are not wrong — they may be necessary for post-2050 deep decarbonization. But as near-to-medium term strategies, they cannot compete with the economics of making the existing fuel system work better through specification reform.

The key insight: Every dollar spent on SAF spec reform delivers immediate, fleet-wide emissions reduction using infrastructure that already exists. Every dollar spent on hydrogen or electric aviation requires decades of parallel investment in aircraft, engines, airports, and distribution before a single ton of CO₂ is avoided.

8. Data Sources

Boeing 787 development: Seattle Times ($32B, 2011); industry estimates up to $50B with overruns
Airbus A350: Simple Flying ($12–15B); Airbus A350 Wikipedia
Boeing 777X: Aviation A2Z ($1.5B in added costs from delays alone)
Engine development: CFM/GE/Safran/P&W disclosures; industry analyst estimates ($1.5–3B typical)
Hydrogen aircraft: Transport & Environment / TUHH / Steer (Apr 2023); Airbus ZEROe delays (Reuters, Feb 2025; Flying Magazine, Apr 2025)
Airport infrastructure: WEF/McKinsey "Target True Zero" ($700B–$1.7T, Apr 2023)
IATA hydrogen investment tracking: $4B+ announced to date
FAA certification timeline: faa.gov (5–9 years for new type certificate)
ICAO SAF Rules of Thumb: WSU/Hasselt University for CAEP

Draft — Feb 21, 2026. Pre-publication. Do not distribute.