A new, “realistic” timeline for achieving net zero carbon emissions in the aviation industry is needed, and the previous target of 2050 will probably not be achieved, according to the head of IATA.

Willie Walsh, the director general of the International Air Transport Association, said “hope was fading fast” and a new “realistic timeline” should be established.

The Guardian reports that the collective goal to eliminate net carbon emissions was declared by global airlines only five years ago in 2021, with similar pledges made by national aviation industry leaders and governments, including in the U.K., in 2020.

Speaking at the annual IATA summit in Rio de Janeiro June 8, Walsh laid most of the blame for the likely failure on fuel suppliers, governments and aircraft manufacturers. More than half of the planned decarbonization of aviation was dependent on the development of sustainable aviation fuels (SAF), with much of the rest reliant on a global emissions trading program, Corsia, established under by the UN and its aviation body ICAO. But Corsia was being “undermined” by government inaction, while annual production of SAF would only reach 2.4 million tonnes, or 0.8% of airline fuel needs, this year, Walsh said. “The goal is 65% or 500m tonnes by 2050. The gap is wide and not closing fast enough.”

Walsh told the Guardian later that airlines were “continuing to do everything we said we would do, but we can’t achieve net zero in 2050 on our own.”