AI needs a lot of energy, and from Sam Altman, to Bill Gates, to Peter Thiel, tech billionaires with heavy involvement in AI tend to also invest in the futuristic energy moonshot that is nuclear fusion. But the giant, energy-sucking data centers of today are powered by the energy sources of today, including—it turns out—sputtering old repurposed airplane engine cores.

As noticed by IEEE Spectrum’s Drew Robb earlier this week, Missouri-based company ProEnergy is doing healthy business by supplying used General Electric CF6-80C2 jet cores, which are “high-bypass turbofan engines” according to a PDF on the GE aerospace website, to data centers that are so desperate for energy they can’t wait for power utilities to supply it.

These babies were designed to propel 767s through the sky, but with the right modifications, they can be locked down on concrete slabs or packaged into trailers, wired up to data centers, and dialed up to 48 megawatts of power generation. If my numbers are right (and here’s where I’m getting them) that’s enough to power about 32,160 American homes. Or, perhaps, an AI cluster.

ProEnergy’s commercial operations VP Landon Tessmer spoke to IEEE Spectrum’s Robb at the World Power show in San Antonio earlier this month, telling him that 21 such aviation engine generators have been sold to data centers for use during construction. They’ll be the intended power source for years after these centers are up and running, Tessmer explained, and have the potential to become backup generators once grid power is in place.