Jet A-1 Fuel Standards: ASTM D1655 vs DEF STAN 91-91 for Aviation Procurement

Jet A vs Jet A-1: The Critical Difference

• Jet A — Used domestically in the US. Freeze point max −40 °C.
• Jet A-1 — International standard. Freeze point max −47 °C. Used everywhere outside the US.

For any flight that crosses oceans or operates in cold-soak conditions, Jet A-1 is required. Procurement teams supplying international airline operations should default to Jet A-1.

The Two Governing Specifications

ASTM D1655

Issued by ASTM International. Defines Jet A and Jet A-1 requirements: distillation curve, freeze point, flash point (≥38°C), smoke point, sulfur (≤0.3% wt), thermal stability (JFTOT).

DEF STAN 91-91 (formerly DERD 2494)

UK Ministry of Defence standard. Slightly stricter than ASTM D1655 on several parameters, particularly thermal stability and additive requirements. Widely adopted by IATA Joint Inspection Group as the de facto global standard.

Required Additives

DEF STAN 91-91 mandates:

• Static Dissipator Additive (SDA) — prevents fuel-handling static buildup
• Fuel System Icing Inhibitor (FSII) — typically Di-EGME (military only; FSII is optional in commercial Jet A-1)
• Antioxidants — required for hydrotreated fuels

Procurement Documentation

Every batch of Jet A-1 must arrive with: 1. Refinery Certificate of Quality (RCQ) referencing specific spec version 2. Recertification Test Certificate (RTC) if held in storage > 6 months 3. Joint Inspection Group (JIG) Bulletin compliance statement 4. Material Safety Data Sheet (MSDS) per GHS

Common Off-Spec Issues

• Particulate contamination from storage tank rust
• Microbial growth at the fuel-water interface in poorly drained tanks
• Freeze point drift from blending with kerosene of inconsistent origin
• SDA conductivity failure — additive degrades over time

Procurement teams must specify recertification testing if any cargo will sit in storage >6 months, and require a fresh CoQ before release.

Bottom Line

For international aviation operations, specify Jet A-1 to DEF STAN 91-91 Issue 8 (current) or ASTM D1655 Latest Revision, with full additive package and recent recertification. Anything less invites operational risk that no per-tonne discount can offset.