Image copyright Airbus

Airbus, Rolls-Royce and Siemens are to develop hybrid electric engine plane technology as part of a push towards cleaner aviation.

The E-Fan X programme will first put an electric engine with three jet engines on a BAe 146 aircraft.

The firms want to fly a demonstrator version of the plane by 2020, with a commercial application by 2025.

Firms are racing to develop electric engines for planes after pressure from the EU to cut aviation pollution.

Each of the partners in the programme will be investing tens of millions of pounds, they said on a press call.

The firms are developing hybrid technology because fully electric commercial flights are currently out of reach, a spokeswoman said.

The weight of batteries coupled with the weight of equipment to cool electric engines are two limiting factors at present, she said.

"We see hybrid-electric propulsion as a compelling technology for the future of aviation," said Paul Eremenko, Airbus' chief technology officer.

Image copyright Airbus

Rolls-Royce will be providing the electricity generator at the back of the E-Fan X plane.

The turbine powering the generator will run on jet fuel and provide power for the electric engine.

Any excess power from the generator will be stored in banks of batteries in the fore and aft holds with the stored energy to be used during take-off and landing.

A Rolls Royce spokesman said the company wanted to make the turbine as light as possible, and that "parts of the engine, generator and power electronic systems will be integrated to reduce weight."

Analysis: BBC business reporter Theo Leggett

There are several good reasons why Airbus wants to develop electrified planes.

Jet fuel makes up a significant proportion of a typical airline's running costs - over the past few years it has varied from 17-36%, depending on the price of oil. Use less fuel and costs should come down.

Then there's noise. Modern jets aren't nearly as noisy as their predecessors from a couple of decades ago, but they still make quite a racket on landing or takeoff. If your house is close to the airport that's bad news.

Electric motors are a lot quieter, so they could allow more night flights, especially in airports close to city centres.

And of course, there's the question of emissions. Electrified aircraft, like hybrid cars, should be cleaner than conventional models.

With some forecasts suggesting the number of large aircraft will double over the next 20 years, they could become a powerful tool for cutting emissions of NOx and CO2.

So the potential benefits are clear - but first the technology needs to be proven.

Electric race

The E-Fan programme began in 2012 with a collaboration between Airbus and Rolls-Royce.

As part of its Flightpath 2050 plan, the European Commission wants a reduction of carbon dioxide emissions by 60%, it wants nitrogen oxide pollution down by 90%, and noise reduction of 75%.

That has been one of the driving forces behind the Airbus, Rolls-Royce and Siemens programme.

Other firms are also working on commercial passenger electric plane flight.

Easyjet wants electric planes to fly passengers on its short-haul routes, possibly within 10 to 20 years.

And Wright Electric is aiming to offer an electric-powered commercial flight from London to Paris in 10 years.