The Pentagon has deployed a WC-135W Constant Phoenix, a modified Boeing C-135 equipped to detect radioactive clouds, to identify radiation leaks from the damaged Fukushima nuclear plant in Japan.

The aircraft, similar in size to a Boeing 707 airliner, is designed to collect particulates and whole-air samples for radiation testing from the Pacific region.

The craft is usually used for monitoring required by the 1963 Limited Nuclear Test Ban Treaty, which prohibits above-ground nuclear weapons testing, according to Bloomberg.

The WC-135W, which replaced the WB-50, has come into existence since the 1947 programme commissioned by General Dwight D Eisenhower for detecting atomic explosions.

The deployment of the aircraft will provide humanitarian and technical assistance to Japan after the 11 March earthquake, tsunami and the subsequent nuclear disaster.