Honda has announced its withdrawal from Formula 1 at the end of the 2021 season, a decision that leaves Red Bull Racing and AlphaTauri in need of new engine partners from 2022.
Honda returned to Grand Prix racing in 2015 with McLaren, but the three-year partnership was an unmitigated disaster and led the Japanese manufacturer to transfer its engines to Toro Rosso in 2018, before adding Red Bull to its supply a year later.
Honda enjoyed success with the Milton Keynes-based squad, winning four races with Max Verstappen, including this year's 70th Anniversary race at Silverstone, while AlphaTauri's Pierre Gasly tagged on another win at Monza.
However, the automobile industry's paradigm shift to electric mobility coupled with the sector's current economic difficulties has dissuaded Honda to extend its involvement in F1 beyond next season.
In a statement Honda said: "Honda needs to funnel its corporate resources in research and development into the areas of future power unit and energy technologies, including fuel cell vehicle (FCV) and battery EV (BEV) technologies, which will be the core of carbon-free technologies."
Despite Honda's future retreat from the sport, Red Bull team boss Christian Horner said the energy drink company remained committed to F1.
"As a Team we understand how difficult it has been for Honda Motor Company to reach the decision to step back from Formula One at the end of the 2021 season," said Horner.
"The shifting focus within the automotive industry has led to Honda’s decision to re-deploy their resources and we understand and respect the reasoning behind this.
"Their decision presents obvious challenges for us as a Team but we have been here before and with our strength in depth we are well prepared and equipped to respond effectively, as we have proven in the past.
"Whilst we are disappointed not to continue our partnership with Honda, we are enormously proud of our joint success, delivering five wins and 15 podiums for both Red Bull owned teams and we thank everyone at Honda for their extraordinary efforts and commitment," added Horner.
"Our joint focus for the remainder of the 2020 and 2021 seasons are unchanged, to fight for victories and challenge for the championship.
"As a signatory to Formula One’s latest Concorde Agreement, Red Bull Racing remains committed to the sport in the long term and we look forward to embarking on a new era of innovation, development and success.
"As a group, we will now take the time afforded to us to further evaluate and find the most competitive power unit solution for 2022 and beyond."
Honda's withdrawal will leave just three engine suppliers in Formula 1: Mercedes, Ferrari and Renault.
Red Bull's acrimonious split with Renault at the end of 2018 implies that a revival of the partnership between those two parties is unlikely.
However, the French manufacturer will be without a partner in 2021, as McLaren will be switching its allegiance to Mercedes. Also, the FIA could force Renault's hand in compliance with F1's engine supply rules that compel a manufacturer to supply a team that finds itself without an engine deal.
Queried last weekend in Russia about its engine supply plans in the future, Renault F1 boss Cyril Abiteboul commented:
"We are open to opportunity, but it’s not like we are actively searching for opportunities simply because we have been involved in many customer arrangements and it’s still not that clear cut that it’s bringing you something that you really need in order to meet your sporting targets."
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