A plan by the government to increase the radio exclusion zone around the Square Kilometre Array radio telescope in the Northern Cape has the aviation industry up in arms. The Civil Aviation Authority said the proposed SKA radio protection zone falls within the world's 10th-busiest city-to-city airline traffic route, directly between Cape Town and Johannesburg.Not only are industry experts concerned about the routes, they are also worried about the cost implications. Route changes could mean higher fuel costs.The Department of Science and Technology has proposed legislation for the development of the Karoo Central Astronomy Advantage Areas. It will be up for public debate next month.If passed, the law will see a vast radio "quiet" - or protection - zone established across the Northern Cape. At the centre of the zone is the SKA project near Carnarvon, which will, by the time construction is completed in 2025, consist of more than 200 specialised radio antennas.The SKA forms part of a larger scientific astronomy hub spread across Southern Africa. The designated Karoo Central Astronomy Advantage Areas measure 110402km² - one-tenth of the size of South Africa.Australia, also part of the SKA programme, has a radio quiet zone of 212457km².Aviation experts are concerned that, in addition to the Cape Town-Johannesburg route, flights from Cape Town to Kimberley and Upington, and to Namibia and Botswana might be affected.The government proposes that the radio protection zone also extends vertically to 18.5km - twice the height at which commercial airlines fly.The government has so far dismissed the concerns.But CAA spokesman Kabelo Ledwaba said a ban would have dire consequences for all aviation activities and might see the country failing to comply with international aviation standards."It's alarming that although the authority contributed to the development of the act its input was omitted from the act. The aviation industry and the CAA are advocating for changes to the law."Ledwaba said the SKA's core area - the Karoo Central Astronomy Advantage Areas - was the biggest concern for aviation."The area is enormous. It lies adjacent to and below heavily populated air traffic routes between Johannesburg and Cape Town."Such routes result in large amounts of electronic transmissions by aircraft. Reducing or not interfering with the SKA's monitoring activities means a flight operating at 35000ft must be routed, at the very least, via Port Elizabeth and then seawards off the coastline to Cape Town to respect the radio quietness required," Ledwaba said. "We are vigorously debating the proposed aviation restrictions with the department."Freight transport companies' vehicles use special radio communication systems that could also be affected.The department believes the effect would be minimal.Department spokesman Lunga Ngqengelele said: "The declaration of a radio quiet zone doesn't automatically impose restrictions on the use of air space."If any are required these would be spelt out in appropriate regulations. Aircraft use radio frequency devices which may cause harmful radio frequency interference to the telescope, if not properly managed."He said: "The effect on air traffic will depend on the type of traffic."Ngqengelele said there would be no blanket restrictions on the use of cellphones in towns within the area although, in the immediate vicinity of the radio telescopes, people would have to turn off phones.Both Vodacom and MTN said they were working closely with the government to find ways to mitigate the electromagnetic interference cellphone radio signals would have on the SKA.SKA spokesman Lorenzo Raynard said there was a need to protect the area."The instruments are highly sensitive and can be damaged and radio astronomy observations affected. These interferences could include radio transmissions from broadcasters and radio noise produced by electrical devices such as microwave ovens."The highest level of restrictions will be closest to the SKA's core. But this does not mean that all radio signals will be banned."He said special software would be used to eliminate radio frequency disturbances from aircraft travelling at high altitudes, but low-flying aircraft would not be allowed to fly directly across the antennas."Freight transport can operate in the area using their radio communication systems as long as their technology uses frequencies outside the restricted bands."Private pilot James Pitman said the "protection" zone would have an immense effect on private pilots' business operations: "Aircraft not only have verbal communication systems, but also radars and transponders which emit signals."..