Predicting increased risks to air travelers from solar activity, NASA is developing a system to predict radiation entering Earth's atmosphere from space.

The goal is to provide high-flying commercial airline passengers and crew with real-time information about the radiation they will be exposed to in flight.

"Aviation occupational radiation exposure currently is not monitored, measured and quantified. This will be the first model of its type to do that," said scientist Chris Mertens of NASA's Langley Research Center.

Exposure to radiation has been shown to increase health risk, according to numerous studies. Space radiation on the ground is very low, but increases significantly with altitude. At 30,000 to 40,000 feet, the typical altitude of a jetliner, exposure on a typical flight is still considered safe - less than a chest X-ray. Exposure is considerably higher, however, over the Earth's poles, where the planet's magnetic field no longer provides a shield. And with a thousandfold rise in commercial airline flights over the North Pole in the last 10 years, exposure to radiation has become a serious concern, NASA has said.

Researchers have expressed serious concerns over long-haul flights since the sun has been in a "grand solar maximum" that has already lasted longer than another other maximum in the past 9,300 years.

NASA says a study by Mertens of polar flights during a solar storm in 2003 showed that passengers received about 12 percent of the annual radiation limit recommended by the International Committee on Radiological Protection. Airlines save huge amounts of fuel by flying "over the top" routes because they are the shortest way between certain points, such as North America and Asia. They also pass through weaker headwinds, saving even more fuel.

Cosmic rays from deep space and high-energy particles from the sun are hazardous to astronauts and are likely to expose airline crews and passengers to high levels of radiation researchers have said. Cosmic rays constantly hit Earth, but the solar activity is dependent on the sun's regular "weather cycle." NASA expects the maximum to reach its peak in 2013 and the fade.

The study says that at cruise altitudes of commercial aviation, particularly at higher latitudes, high-energy ionising radiations such as Solar Energetic Particles and Galactic Cosmic Rays pose threats through upsets in electronics critical to flight safety, and through the radiation exposure of crew and passengers.

The International Commission on Radiological Protection recommends a 1 mSv limit for the annual dose. Dosages during a flight depend on path, duration and altitude as well as on the level of solar activity. A commercial eight-hour polar flight during the 2003 "Halloween" SEP event would have given 70 percent of this recommended annual limit and it is estimated that the largest known SEP event, the "Carrington event" of 1859, would have given 20 times the limit.