The US Air Force (USAF) has decided to scrap its plans to replace the Cold War-era U-2 spy planes with Northrop Grumman-built Block 30 high-altitude RQ-4 Global Hawk unmanned surveillance planes, a government official and a defence analyst have revealed.

Virginia-based Lexington Institute CEO Loren Thompson said that details of how many Global Hawks the Air Force has decided to scrap were not clear but indicated that building on the aircraft will stop with immediate effect and that the existing planes in the inventory would be retired. The air force planned to purchase 42 Block 30 aircraft, with the cost of each aircraft estimated to be around $215m, according to 2011 budget documents. However, the Global Hawk programme is expected to be terminated in the Pentagon’s fiscal year 2013 budget request and five-year plan.

The plan, if approved by Congress, will bring down the number to 21 planes, ten less than currently planned. The USAF has already received 14 of the Global Hawk Block 30 drones from Northrop, which is under contract for four additional planes, with three planes already funded. Northrop said that it has not yet received any notification regarding the changes to its Global Hawk contract.

Reuters previously reported USAF Chief of Staff general Norton Schwartz as saying that the budget proposal for fiscal year 2013 would seek to terminate some programmes, while questions relating to the "cost and effectiveness of the Global Hawk" still remained. Northrop’s RQ-4 Global Hawk was due to replace the Lockheed U-2 spy plane in 2015, but would now be kept in service until 2023.

The remotely piloted RQ-4 Global Hawk is a high-altitude, long-endurance unmanned aerial reconnaissance system, which provides military field commanders with high-resolution, near real-time imagery of large geographic areas.