When the FAA released its draft unleaded avgas transition plan in January, we found a useful framework wrapped around a collection of unanswered questions. The draft described four phases leading to the elimination of 100LL by the end of 2030 outside Alaska, but left uncertain when rulemaking would begin, how much unleaded fuel availability would be enough, what the transition might cost aircraft owners and what would happen if several approved fuels could not peacefully coexist in the same national fuel system.
Six months later, the FAA’s published Version 1.0 is a better document. It is more specific about several of those risks and, in some cases, turns vague possibilities into concrete work the agency says it will perform.
What it does not do is provide the complete national transition schedule that its title might suggest.
The FAA now says explicitly that it cannot develop that plan until more information is available. Version 2.0, expected after Phase 1 concludes in late 2027, is supposed to define the schedules and activities for Phases 2 through 4.
Some January Questions Have Better Answers
Commentary around fuel compatibility is the clearest example of progress, at least around clarification. The draft acknowledged the potential problem created by multiple unleaded fuels and said the FAA might conduct intermixability testing. We noted as much when the draft was released in January, pointing out that several fuels approved for the same airplane could create confusion and misfueling concerns if they could not be safely mixed.
The new plan removes much of the ambiguity around the question itself.
All three candidate fuels are approved, or are seeking approval, to mix individually with 100LL. The fuel developers do not currently support mixing their unleaded fuels with one another, though.
The FAA now says it will conduct commingling testing during Phase 1. More importantly, it explains the consequences if that testing does not produce a workable solution: regional fuel markets could fragment, misfueling risk could increase and an airplane’s authorized fuel might not be available along a planned route.
That is an important advance over the draft. While still not a particularly satisfying answer, the FAA at least acknowledges that it does not know whether the fuels can be mixed and, most significantly, treats the answer as something the national transition depends upon.
Rulemaking has also become somewhat clearer. The draft said the exact timing could not be determined until the transition had progressed far enough. Version 1.0 says the FAA expects to initiate the required rulemaking during Phase 2, after it has data on the candidate fuels and some initial operating experience. The proposed rule could address the Phase 3 and 4 schedules, regulatory costs and alternatives.
Cost received a similar treatment. The January plan listed STCs, aircraft modifications, infrastructure and fuel-price differences among potential expenses. The new version goes further and acknowledges that the FAA does not yet know the extent of modifications individual airplanes may require, what those modifications will cost or how those costs ultimately will be divided among aircraft owners, fuel companies and government entities that elect to subsidize portions of the transition.
Again, while not a satisfying resolution, it is good to at least see the issue acknowledged and the uncertainty stated plainly, along with the consequences.
Unanswered Questions
One of our larger concerns in January was availability. The draft assumed that one or more unleaded fuels would be broadly available before the national transition, but provided no measurable standard for what “available” meant. It did not say how much production capacity, how many airports or what geographic coverage would be enough before 100LL could disappear.
Version 1.0 still does not.
Instead, the FAA used the final version to illustrate what failure could look like. One of its Phase 3 scenarios assumes several incompatible fuels remain on the market, different airplanes require different alterations and airports select fuels independently. The agency identifies the resulting problems directly, including fragmented markets, complicated distribution, in-transit refueling problems and insufficient tank capacity that reduces the geographic availability of suitable fuel to an individual operator.
That scenario acknowledges one of the most practical questions any one of us might eventually be forced to ask in that scenario. “Can I leave home knowing the fuel my airplane requires will be available where I am going?”
That is helpful insofar as the plan at least recognizes that problem. But again, it does not do so in a particularly satisfying way at this stage, because at least for now, it does not establish the conditions that must be met before the answer can safely become “yes.”
The same applies to airplanes requiring modifications. The plan acknowledges that some aircraft may need more than paperwork and placards before they can use a replacement fuel. It repeatedly identifies the lead time and cost of any necessary aircraft alterations as a transition issue. Still, it does not seem to address what happens if the necessary modifications are unreasonably difficult or economically impractical.
Version 1.0 establishes no general hardship provision, permanent 100LL exception or owner-assistance program for that situation.
Nor has the FAA committed to making every airport support every fuel. And while we, as pilots and aircraft owners, would be likely best served if that was the case, it is unfortunately understandable why the FAA can make no such commitment.
The plan continues to recognize the reality that many airports have infrastructure for only one grade of avgas. Its Phase 3 scenarios envision airports and FBOs selecting fuels for their individual locations. Temporary tanks, trucks and other equipment may make the transition easier in some places, but a nationwide network in which every piston airplane can readily find its approved fuel remains a desired outcome rather than a defined requirement.
Assuming (as might reasonably be the case in practice) that not all unleaded fuels are cross-compatable in every aircraft, that reality has the capability to severely limit the usefulness of a presently unknown chunk of our existing national GA fleet.
The Final Plan Is Really a Plan to Finish the Plan
Yes, that’s a bit of a mouthfull. But that is probably the most significant change from the draft to the final plan. Today’s final plan is not, in fact, the final plan. It is a way forward, but it absolutley must be updated, and thankfully it does anticipate that.
The draft presented four phases and left many details blank. Version 1.0 is more forthright about why those blanks exist. The FAA identifies fuel production, infrastructure, fleet readiness and supporting policy as four items on the transition’s critical path. A substantial delay in any one can threaten the entire schedule. It calls scheduling the transition’s most potentially significant risk and says the next version will use Phase 1 results and early Phase 2 experience to develop a realistic future schedule moving forward.
The FAA also noted that public comments (which have yet to be publicly released, by the way) focused on aircraft modifications, mixing unleaded fuels, regulatory timing and cost. Many of those subjects remain under development and are expected to be worked through during Phase 1. The agency intends to issue continuing updates, a public FAQ and a separate summary explaining how substantive comments on the draft were handled.
In that sense, Version 1.0 is a step forward. It separates questions the FAA can answer now from questions that depend on data nobody has yet.
And of course, the answers to those questions are very much interconnected.
Fuel compatibility affects airport infrastructure. Infrastructure affects geographic availability. Availability determines which fuel an owner may realistically have to use. That choice determines potential aircraft alterations and cost. Production has to expand quickly enough to supply whatever market emerges, while FAA rulemaking has to arrive at the right point in the process.
Very little can be settled independently.
What Comes Next
The FAA does not necessarily need another layer of objectives at this point. They do seem to be aware of the major issues and to be asking most of the right questions of the process’ future. The existing plan identifies most of the major technical and market problems that stand between today’s 100LL system and a national unleaded system.
What it needs now are meaningful decision points. How do we know when an objective has been achieved, in the FAA’s eyes?
Before the national transition begins, we need to know what the FAA believes constitutes adequate fuel availability, how incompatible fuels would be managed if commingling proves impractical, how much notice airports must provide before changing fuels and what happens to aircraft that cannot reasonably use the replacement available at a particular airport.
Airports and FBOs need enough information to make infrastructure decisions without betting on a fuel that later becomes commercially marginal. Fuel producers need a transition schedule capable of supporting investment in production and distribution.
And everyone needs to know soon enough for those decisions to be made well before 2030, rather than on the fly under the pressure of looming deadlines.
The published plan does not provide that.
That makes late 2027, and Version 2.0, incredibly consequential. By then, the FAA expects to have comparative fuel data, a better picture of compatibility and aircraft alterations, and enough market experience to start turning scenarios into schedules.
Version 1.0 has done a better job than January’s draft when it comes to defining problems and explaining some of the thought processes behind the plan. Version 2.0, though, will have to show exactly how and when the rubber hits the road, and will need to bake in plenty of lead-time for that to be done effectively.
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