STEADY IMPROVEMENTS in battery technology, driven along by the electrification of road transport, are helping air taxis and other small electric aircraft get airborne. But even the best lithium-ion cells are still far from being able to power the workhorses of civil aviation: short-haul airliners carrying 150 or so passengers. An electric version would not be able to rise from the ground, because of the weight of the batteries required to drive its engines. Nevertheless, many aerospace experts continue to think that electric flight is the future, at least in hybrid form.
This could be achieved by starting with smaller hybrid airliners, such as those carrying 50 or so passengers on regional routes, and then scaling the technology up. Details of one such effort, called Project 804, illustrate how the airborne equivalent of a hybrid Toyota Prius might work.