Denver's Centennial airport is celebrating the two-year anniversary of its unleaded aviation fuel programme, becoming the first airport in the state of Colorado to offer Swift UL94, a FAA-approved unleaded aviation fuel for piston aircraft.

Since May 2023, UL94 has been available at the jetCenters of Colorado's Centennial location. Centennial airport's transition to unleaded fuel began with a resolution passed by the Arapahoe County Public Airport Authority board of commissioners in March 2023, authorising incentives to accelerate the switch from 100LL (low-lead) to FAA-approved unleaded alternatives.

As part of the airport's initiative, Centennial offers an STC reimbursement programme, reimbursing up to $110 per aircraft to cover the cost of FAA approval for using UL94, and a fuel subsidy programme that bridges the price gap between 100LL and UL94 for fuel suppliers and users.

To date, the airport has reimbursed 105 STC applications and has seen UL94 account for over 20.5 per cent of all aviation fuel for piston aircraft sold at Centennial since its introduction (Jet A, used in turbine aircraft, is already unleaded). Prior to receiving state support, the airport independently invested over $304,000 in fuel subsidies and STC reimbursements.

The programme's success has helped position jetCenters of Colorado at Centennial airport as the largest FBO user of UL94 in the country, a testament to the commitment from both the airport and its tenants. “We are proud to be a large part of Centennial airport's environmental sustainability,” states Tony Buckley, president and CEO jetCenters of Colorado.

Centennial's leadership has also been recognised by the Colorado Aeronautical Board, which approved two discretionary grants of $300,000 in 2024 and $350,000 in 2025 to further support the airport's fuel subsidy programme. These grants were made possible by Colorado House Bill 24-1235, signed into law by Governor Jared Polis in May of 2024, which authorised the CAB to distribute funding for unleaded aviation fuel initiatives. Centennial Airport contributed a 10% match to both grants, reinforcing its financial commitment to the transition.

“Environmental sustainability is a key priority at Centennial airport,” says Mike Fronapfel, airport CEO. “This programme is our way of supporting industry-wide efforts to eliminate lead emissions without compromising aircraft performance or safety. It also reflects our commitment to listening to the concerns of our surrounding communities and responding with meaningful action.”

Aspen Flying Club was the first to convert its Centennial airport-based fleet to Swift UL94 and remains the airport's largest user of the unleaded fuel. “As the operator of the largest fleet of aircraft in Colorado, we are always looking for ways to improve our services through new technologies,” comments Danny Smith, president of American Flight Schools. “The adoption of unleaded fuel has had the most positive impact on reducing maintenance costs, with a noticeable drop in unscheduled maintenance issues directly tied to no longer using leaded fuels.”

The initiative aligns with the FAA's EAGLE (Eliminate Aviation Gasoline Lead Emissions) initiative, which seeks to eliminate leaded fuel in piston-engine aircraft by 2030. Swift UL94 is a FAA-approved, drop-in-ready unleaded aviation fuel that meets or exceeds ASTM standards, offering identical density and performance to 100LL without the environmental drawbacks of lead.