There’s a kind of beauty in electric planes you don’t get from their gas-powered counterparts. They’re quiet. They don’t vibrate or require expensive fuel. They're great for training pilots.

So you’d think we’d have lots of battery-powered airplanes on the market by now, but we don't. The reason, according to industry insiders, is not because of technological issues or safety concerns.

It’s because of a single phrase in the government’s seemingly endless list of rules that must be followed to certify a new airplane design as safe to fly. The rule was written before electric powerplants for aviation were taken seriously, but the government won’t change it.

In 2004, the Federal Aviation Administration created a new category of airplanes, called Light Sport Aircraft (LSA), to make it easier and cheaper for manufacturers to certify simple, fun-to-fly airplanes.

The new rules have allowed for the creation of dozens of new two-seat airplane designs. None of these are electric, however, because in the preamble to the rule, the FAA wrote that all planes in this class must have “a single, reciprocating engine, if powered.”

The point of the rule, FAA officials acknowledge, was to keep more powerful turbine engines out of the picture. The banning of electric powertrains is unfortunate collateral damage.

"This is the thing that has scuttled electric aircraft's significant development, for years," says Dan Johnson, president of the Light Aircraft Manufacturing Association, a trade group. "Just by changing six or eight words, you could undo the problem — but we can't get there."

Manufacturers are ready to move forward, pilots are ready to buy. The small two-seat sport airplanes are light enough to be powered by batteries similar to the ones in cars. The costs to develop and certify new aircraft are manageable; and the market is big enough to support those costs.

The rules have kind of frozen innovation. It's hard to make the business case. Greg Bowles, General Aviation Manufacturers Association

The barrier to progress is that one clause. There's plenty of interest from buyers and from manufacturers, Johnson says, but they're stymied by that rule. The FAA is a bulky, slow-moving bureaucracy, where rules can take years to change, but Johnson says this issue, given the wide interest and the fast-developing technology, is especially frustrating.

And while Johnson and others in the industry say the FAA employees they interact with are generally supportive of their electric ambitions, the official FAA position is not so innovation-friendly. “LSAs were meant to be simple, two-place, recreational aircraft that are simple to operate and maintain, and therefore do not require design or production approval,” the FAA says. “The technological and training issues for certification and operation of electric engines go beyond the intent for simple, easy-to-maintain, recreational aircraft.”

Bigger private airplanes, with four to six seats or so, are certified under different, more complex rules, called Part 23. Those certification costs ring in around $10 million or more, compared to about $200,000 in the sport category. So it’s no surprise progress has slowed. "It's gotten more and more difficult to innovate," says Greg Bowles, of the General Aviation Manufacturers Association trade group. "The rules have kind of frozen innovation ... It's hard to make the business case."

But paradoxically, major revisions now in the works for Part 23 may end up allowing the bigger airplanes to use electric powerplants sooner than the sport planes. Bowles hopes the revisions will be done in two or three years. "These new rules will allow us to evolve the way we should be evolving,” he says. “We're removing unintended consequences while keeping safety in place."

Meanwhile, innovators continue working to develop electric technology for airplanes. Ultralight and experimental aircraft already are allowed to use electric powerplants, but those products appeal to a smaller niche of pilots. In Europe, a number of small electric airplanes already are on the market, with Pipistrel leading the way.

Airbus is working on two new designs, including a four-seat hybrid. Aero Electric Aircraft Corp., based in Denver, is working to certify its two-seat Sun Flyer under a seldom-used part of the FAA rules for "primary airplanes," which allows for electric powerplants but requires a more complex and costly certification process than the LSA category.

Bowles is hopeful the revised Part 23 rules now in the works will free up the pace of innovation. "The good news is, we're going to see significant improvements in safety, in utility, and in the variety of aircraft on the market,” he says. While pure battery-electric flight may be a ways off for these bigger airplanes, there’s a lot of interest in developing hybrid systems once the new rules are in place.

Those who value the experience of flight as something more than just getting from A to B aren’t going to give up, and one way or another, they’ll find a way forward. "I've flown in an electric experimental airplane, and they're kind of magical,” Johnson says. “You can hear things on the ground, while you're flying."