Plane takes flight over Washington, with no fuel. (It's electric.)

A plane retrofit with an all-electric motor successfully took flight over Washington for 30 minutes on Thursday.

The small plane, a Cessna Caravan, used a MagniX 750-horsepower motor in the test flight, the same type of MagniX engine installed on an all-electric seaplane that flew over British Columbia in December. The aviation company AeroTEC modified the Cessna.

Electric planes, after further testing, may one day prove successful in transporting people on shorter regional hops (perhaps some 300 miles or less). That's good, because taking off burns a lot of fuel, meaning short flights today have double the "carbon intensity," or amount of carbon burned per mile, than longer flights.

But all-electric motors won't replace the engines on big commercial jetliners for at least many decades, if ever. "Will [electric motors] replace jet travel? No," Bob van der Linden, an aviation expert at the Smithsonian Institution's National Air and Space Museum, told Mashable in December.

Even major airlines acknowledge that jet fuels are the future (though perhaps airlines will gradually adopt lower-carbon fuels). That's because long electric flights would require giant batteries, making the planes much too heavy to fly, explained van der Linden.

(This all-electric Cessna test flight couldn't fit any passengers, the Seattle Times reported, because battery equipment filled up the plane.)

Overall, airplanes have an outsized role in emitting carbon into the atmosphere, as planes contribute over two percent of total annual global carbon emissions — more than most nations in the world. "Someone flying from London to New York and back generates roughly the same level of emissions as the average person in the EU does by heating their home for a whole year," the European Commission notes. Regional flights account for about 5 percent of aviation's carbon emissions.

But with electric planes, these flights could at least one day make a dent in the heat-trapping carbon emissions emitted from aircraft. After all, it's going to take an unprecedented, diverse effort to curb the planet's relentless warming trend: 19 of the last 20 years are now the warmest on record. Earth's warming atmosphere is reacting to a skyrocketing rise of the potent greenhouse gas carbon dioxide — now at its highest levels in at least 800,000 years, but more likely millions of years.