Saudi Arabia is joining seven other nations (Brazil, Greece, Mexico, Pakistan, Sweden, Thailand and the United Arab Emirates) by ordering six Swedish Erieye aerial surveillance systems. Erieye is a very economical and effective AEW (airborne early warning) aircraft. A year ago, neighboring UAE (United Arab Emirates) bought two of them.
The Erieye system consists of a Saab 2000 (an advanced version of the Saab 340 airliner) mounting a Swedish Active Electronically Scanned Array (AESA) radar (which consists of thousands of tiny radars that can be independently aimed in different directions). This is similar to the AESA radar used on the American JSTARS aircraft, enabling it to locate vehicles moving on the surface. The Swedish AESA is cheaper, because it's built like a long bar, mounted on top of the aircraft. This means the radar can only see, in a 120 degree arc, off both sides of the aircraft. A 60 degree arc in the front and back is uncovered. The Erieye radar is optimized for finding aircraft in the air. It can spot large aircraft out to nearly 500 kilometers, and more common fighter sized aircraft at about 300 kilometers.
The Saab 2000 is a 22 ton, twin prop aircraft, with a cruising speed of 660 kilometers an hour. The aircraft can stay in the air about four hours per sortie. The Ericsson PS-890 Erieye radar can also spot ships at sea, and thus can also fill in for maritime reconnaissance duties. The Saab 340 has been in use by the Swedish Air Force since the 1990s.