A phone app that tracks planes can be a new aid to terrorists

The Plane Finder AR application, developed by a British firm for the Apple iPhone and Google's Android, allows users to point their phone at the sky and see the position, height and speed of nearby aircraft.

It also shows the airline, flight number, departure point, destination and even the likely course -- the features which could be used to target an aircraft with a surface-to-air missile, or to direct another plane on to a collision course, the 'Daily Mail' reported.

The programme, sold for just 1.79 pounds in the online Apple store, has now been labelled an 'aid to terrorists' by security experts and the US Department of Homeland Security is also examining how to protect airliners.

The new application works by intercepting the so-called Automatic Dependent Surveillance -- Broadcasts (ADS-B) transmitted by most passenger aircraft to a new satellite tracking system that supplements or, in some countries, replaces radar.

British and European air traffic control systems have not yet adopted the technology but it is being fitted in all new aircraft, which now constantly broadcast their positions. After the September 11 attacks in America in 2001, a senior Federal Aviation Administration official warned that ADS-B technology could be used by terrorists.

He wrote: "Broadcasting the identity and location of aircraft... would open the door for a terrorist to attack a specific aircraft or airline." The firm behind the app, Pinkfroot, uses a network of aircraft enthusiasts in Britain and abroad, who are equipped with ADS-B receivers costing around 200 pounds to intercept the information from aircraft and send it to a central database.

Conservative MP Patrick Mercer, former chairman of the Parliamentary Counter Terrorism sub-committee, said: "Anything that makes it easier for our enemies to find targets is madness. The Government must look at outlawing the marketing of such equipment."

However, the Hampshire-based firm has gone one step further, marketing a so-called 'Augmented Reality' application because users can point a phone’s camera at the sky and see the precise position of aircraft superimposed on the horizon.

The firm claims more than 2,000 people have downloaded Plane Finder AR from iTunes since its launch last month.

Lee Armstrong, a director of Pinkfroot, said: "We have packaged information that is freely broadcast. We haven’t had any objection from the authorities in the UK or anywhere else in the world."

He added that it had "crossed our minds that a terrorist could use it" and admitted that the firm had built in a delay to try to reduce the risk. He said: "It is only real-time to an extent – it is about 30 seconds behind. If someone really wants to do that [shoot down a jet] they could buy their own ADS-B or radar," he said.

A spokesman for the Department for Transport said: "This application might be new but the ability to track aircraft isn't." Terrorists have launched ground-to-air attacks against commercial jets in the past, most recently in Iraq in 2007. The threat has led to Israeli commercial aircraft being fitted with countermeasures.