The U.S. Air Force is weighing the timelines for the retirement of Block 40 RQ-4 Global Hawk reconnaissance drones by Northrop Grumman [NOC] and the fielding of a classified replacement system.

The Air Force Global Hawk fleet has consisted of four Block 20 RQ-4s, 20 Block 30s and 10 Block 40 aircraft. The service received congressional approval in fiscal 2021 to retire the Block 20s and is asking Congress to allow the service to divest the Block 30s in fiscal 2022, as part of the Air Force effort to shed 201 legacy aircraft to help fund a $2.2 billion requested increase in research and development (Defense Daily, May 28).

At a June 17 Senate Armed Services Committee hearing on the Air Force and U.S. Space Force proposed fiscal 2022 budgets, Sen. Kevin Cramer (R-N.D.) said that the service plans to retire the Block 40 RQ-4s starting in 2025 and asked Air Force Chief of Staff Gen. Charles whether he considers the Block 40 RQ-4 a “sunset” system.

“Not at the moment, senator,” Brown replied. “Part of our process is I want to make sure we have a good transition. As we build a plan and look at the classified system we’re bringing on, what I don’t want to do is leave a gap, and so it’s the balance between our planning factors for the Block 40 and the classified system we’re going to bring on to make sure that we have a smooth transition going forward.”

Section 142 of the fiscal 2021 National Defense Authorization Act (NDAA) called on the Air Force to deliver an airborne ISR plan to Congress by March 30, but Air Force leaders have declined to release or discuss that plan despite congressional direction to prepare an unclassified version (Defense Daily, March 17).

Brown has said that a top service need is for ISR assets able to penetrate high-threat environments. Last month, he said that he wants to get approval to discuss the Air Force’s ISR 2030 Plan in order to build support for it (Defense Daily, May 12).

“Some of the capabilities we have today we’ll still have for a while, but we won’t have as many of them, as I transition to something that has that survivable aspect and can see some denied areas,” Brown said. “That’s the challenge we have right now…If I’m off the coast line, I can only see so deep.”

The Air Force did not respond to a request for comment on the envisioned Block 40 RQ-4 replacement, but the latter may be the classified Lockheed Martin [LMT] RQ-170 or the Northrop Grumman [NOC] RQ-180–both of which feature stealthy flying wings.

“Both RQ-170 and RQ-180 have been identified although there are hardly any details of either,” Steven Zaloga, a drone analyst with the Teal Group, wrote in a June 17 email. “RQ-170 seems too small as a RQ-4 surrogate, and no one really knows the size/capabilities of RQ-180. I would not be the least surprised if the USAF is developing and fielding a stealth alternative/supplement to RQ-4. Whether it is the RQ-180 or some other platform, I have no way of knowing due to the level of secrecy attached to these programs.”