February 1, 2008: Five U.S. RQ-4 Global Hawk UAVs were delivered in 2007. Seventeen are in production, as well as six ground stations for controlling and maintaining the aircraft. All nine of the RQ-4A ("Block 10") aircraft have been built (seven for the U.S. Air Force and two for the U.S. Navy). The ones in production are the larger RQ-4B (block 20, 30 and 40) models.

In the last seven years, RQ4s have flown nearly 20,000 hours, over 70 percent of that combat missions, and many of them from Persian Gulf bases. Some of the more recent models have been able to fly 20 hour missions, land for refueling and maintenance, and be off in four hours for another twenty hours in the sky.

The RQ-4 has been very reliable, with aircraft being ready for action 95 percent of the time. A year ago, the U.S. Air Force has ordered five more RQ-4B Global Hawks, at a cost of $58 million each, and, in effect, approved the new model. This version is larger (wingspan is 15 feet larger, at 131 feet, and it's four feet longer at 48 feet) than the A model, and can carry an additional two tons of equipment. To support that, there's a new generator that produces 150 percent more electrical power.

The first three RQ-4Bs entered service in 2006. At 13 tons, the Global Hawk is the size of a commuter airliner (like the Embraer ERJ 145), but costs nearly twice as much. Global Hawk can be equipped with much more powerful, and expensive, sensors, than other UAVs. These more the double the cost of the aircraft. These spy satellite quality sensors (especially AESA radar) are usually worth the expense, because they enable the UAV, flying at over 60,000 feet, to get a sharp picture of all the territory it can see from that altitude. The B version is a lot more reliable. Early A models tended to fail and crash at the rate of once every thousand flight hours, mostly because of design flaws.