Diesel aircraft engines promise lower fuel burn and cheaper operating costs at a time when every gallon and every kilogram matter in the air. Yet as manufacturers push these powerplants into more ...

OSHKOSH—Piper Aircraft has partnered with jet-fueled, diesel piston-engine maker DeltaHawk to give future buyers of PA-44 Seminoles a way to bypass the looming U.S. transition away from leaded avgas.

Diesel engines are a rarity in aviation history, but they've carved out an interesting niche. While most aircraft rely on gasoline-powered piston engines or jet turbines, diesel has offered some ...