The U.S. Air Force has a complicated relationship with its low- and slow-flying A-10 Warthog attack jet. And that’s putting it mildly. The flying branch has tried more than once to retire the ungainly A-10 in favor of speedier planes, only for lawmakers to block the move.

But on at least one occasion, the Air Force actually defended the heavily-armored, gun-armed Warthog from an unlikely challenger—a modern version of the World War II P-51 Mustang that Congress for some reason really loved.

In 1979, Congress demanded the Air Force test out the tiny Piper PA-48 Enforcer light attack plane—a derivative of the then-39-year-old P-51—as cheaper alternative to the A-10, which was brand new at the time. Five years later, the air service put two Enforcers through their paces.

The test revealed that the Enforcer was clearly incapable of competing with the Warthog.

When they ordered the evaluation, American legislators did point out some real problems over at the Pentagon. “Congress expressed concern with the rising costs, increasing technological sophistication and decreasing readiness of tactical aircraft,” according to the official Enforcer test report, which we obtained through the Freedom of Information Act.

The propeller-driven Enforcer promised to solve one of those problems. Piper claimed the plane would cost just a million dollars and be cheap to maintain.