The once undetectable US stealth bombers may have had their cover blown by a new type of radar that uses mobile phone technology.

Melbourne's Herald Sun reported that the new technology, called passive radar, watches signals from phone transmissions and when a plane passes through, it leaves a hole in the pattern, giving away its location.

However, the passive radar system cannot effectively pinpoint whether a plane is a stealth plane or some other aircraft, although the technology would lead to new stealth research, according to scientists.

The hurdle passive radar technology needs to jump is the complex mathematics necessary to translate mobile phone signals into easy-to-understand blips that move across the computer screen.

"This is another trick that will force stealth researchers to push forward," said Massachusetts Institute of Technology professor of aeronautics and astronautics John Hansman.