During the period between November 18 and November 21, 2017, seven airplanes with civilian
registry identified in Appendix 1 were serviced with jet fuel containing DEF at Eppley Air Field
Airport, Omaha, Nebraska (KOMA). During the same time period, an additional six airplanes
identified in Appendix 2 were serviced using refueling equipment that had been exposed to DEF.
The DEF was inadvertently used instead of fuel system icing inhibitor (FSII) on two refueling trucks
at KOMA and injected into the fuel with each truck’s FSII injection system. Only those airplanes
identified in Appendix 1 received the contaminated fuel, and only those airplanes identified in
Appendix 2 were serviced with refueling equipment that had been exposed to DEF.
DEF is a urea-based chemical that is not approved for use in jet fuel. When mixed with jet fuel,
DEF will react with certain jet fuel chemical components to form crystalline deposits in the fuel
system. These deposits will flow through the aircraft fuel system and may accumulate on filters,
fuel metering components, other fuel system components, or engine fuel nozzles. The deposits may
also settle in the fuel tanks or other areas of the aircraft fuel system where they may potentially
become dislodged over time and accumulate downstream in the fuel system as described above.
Airplanes identified in Appendix 1 have experienced clogged fuel filters and fuel nozzle deposits
that led to service difficulties and unplanned diversions. Airplanes identified in Appendix 2 were
exposed to trace amounts of DEF from residual fuel remaining in the refueling hoses and equipment
and we have not received any service difficulty reports from these aircraft.
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