A fleet of 100 B-21 Raiders would require more tankers than the 20 B-2 Spirits currently in service, as well as a faster fuel transfer rate to reduce the time needed to refuel in the air.
The B-21 Raider, the U.S. Air Force’s next-generation stealth bomber, is making significant progress in its testing phase. As the program moves forward, the U.S. Transportation Command (TRANSCOM) recently emphasized the urgent need for more aerial tankers to support B-21 operations, indicating that current refueling capabilities may not be sufficient for the aircraft’s unique mission profile.
“We got a really deep understanding in terms of how they intend to employ their new aircraft,” said Gen. Randall Reed, Transportation Command chief, after a meeting with Gen. Anthony Cotton, the head of Strategic Command (STRATCOM). “And that will drive a slightly different way in which we are to support them, which actually means that it’s going to be a little bit higher requirement specifically in the fuel transfer.”
A spokesperson later clarified to Aviation Week that the increased need for aerial refueling is related to the size of the planned B-21 fleet, as 100 B-21s compared to the 20 Northrop B-2s will need a larger number of tankers to support operations. Reed also added that he’s working, together with Cotton, to address the B-21’s need for a faster fuel transfer rate.
Designed as a long-range strategic asset, the B-21’s operational concept hinges on its ability to penetrate contested airspace, remain undetected, and conduct precise strikes deep into enemy territory. However, as demonstrated by the 24-hour flights performed with the bombers currently in service, the B-21’s full potential will only be realized if it receives adequate aerial refueling support to sustain its extended missions.
Flight Testing Advances with Minimal Adjustments
Northrop Grumman has recently confirmed that the B-21 is progressing steadily through its flight testing campaign at Edwards Air Force Base, California. The company has adopted a meticulous approach, leveraging ground-based testing and a specialized flying test bed to preemptively resolve software and systems integration issues before the aircraft even took off for its maiden flight.
According to Tom Jones, Corporate Vice President and President of Northrop Grumman’s Aeronautics Systems, the B-21 is now conducting multiple sorties per week, at least two, moving towards the goal of making the new bomber a daily flyer. Jones also added that the B-21’s progress has been ahead of expectations and with a good margin on performance.
Open #B21 #Raider weapons bay doors. 🧐 https://t.co/hVBR8aqGwW pic.twitter.com/0pQOnlOHir
— AirPower 2.0 (MIL_STD) (@AirPowerNEW1) March 7, 2025
Among the few details disclosed by Jones, there was the notable news that the B-21 only required one software change in one year of flight testing. He credited this success to both the ground testing and the over 1,000 flight hours of the test bed.
While specifics on the test objectives remain classified, Air Force officials have indicated that the bomber is meeting or exceeding expectations in key performance areas.
Growing Dependence on Aerial Refueling
Despite its impressive range, the B-21 will still require mid-air refueling to reach its full mission potential, allowing it to strike targets anywhere in the world from its base, instead of being forward deployed. Modern aerial tankers are expected to provide critical support, but concerns have arisen over whether the current tanker fleet is adequate for the demands of B-21 operations.
One of the primary challenges is that many of the Air Force’s tankers, specifically the KC-135s, are aging and are not well-suited for operations in contested airspace. Additionally, the KC-46 program, which should replace both the KC-135 and the retired KC-10, has faced persistent technical issues, raising concerns about its readiness to support next-generation assets like the B-21.
The demand for enhanced aerial refueling capabilities now also raises additional questions about future tanker procurement, especially after the Air Force recommended to terminate the Next-Generation Air Refueling System (NGAS) stealth tanker. This tanker was intended to operate within contested airspace, where the KC-46 can’t, mainly in support of the Next-Generation Air Dominance (NGAD) manned fighter.
Challenges and Strategic Implications
The push for additional refueling assets highlights broader concerns about the Air Force’s ability to sustain operations over vast distances, particularly in a conflict with a peer adversary like China. A war in the Pacific, for example, would place enormous strain on the U.S. military’s aerial refueling fleet.
The vast distances involved would require a robust network of tankers to keep bombers, fighters, and other aircraft operational for extended durations. Also, there is a need for survivable aerial refueling which can support assets closer to the action, while still staying outside the reach of the enemy.
Another challenge is related to the time required for the refueling operation. In fact, an aircraft as large as a bomber would need to stay connected to the tanker well over 10 minutes, making it more vulnerable, as it needs to maintain a very precise position, but also increasing its chances of detection.
Landing for a hot pit refueling might not always be an option, as in the Pacific it would be much easier to find a runway for a tactical jet than one for a bomber. Also, while on the ground for the long refueling operation, the bomber would still be held at risk by ballistic missiles.
Reassessing the Bomber Fleet’s Size
The problems with the less-than-ideal number of tankers would be further amplified with a larger B-21 fleet. In fact, in December 2024, the head of Air Force Global Strike Command (AFGSC), Gen. Thomas Bussiere, said the bomber fleet’s size might need to be reassessed as demand for bombers is growing.
“We have 141 bombers in the inventory, between the B-1, the B-2 and the B-52,” said Gen. Bussiere. “The demand signal for the bombers is greater than any time I’ve seen in my career, across the fabric of every geographic combatant command.”
During 2024, the bomber fleet had to satisfy multiple operational commitments, such as the combat mission of the B-1Bs and B-2As in the Middle East and the B-1B, B-2A and B-52H Bomber Task Forces (BTF) in Europe and in the Indo-Pacific. Because of this, the service could require more B-21 Raider bombers beyond the currently 100 planned, so the bomber force would reach 220 aircraft to satisfy the requirements with 145 B-21s and 75 B-52Js.
“The last 12 months have probably seen the highest level of activity across the globe, both in the European theater and the Indo-Pacific theater,” said Bussiere. “We’ve done more in the last 12 months than I think we’ve done in the last 20 years, with a fleet that’s fairly old and a force that’s fairly stressed based on the demand signal.”
