Reach 4574, a C-17 Globemaster III, flew direct from Kirtland AFB, home to the AFMC Nuclear Weapons Centre, to RAF Lakenheath with the support of KC-46 Pegasus refueling aircraft.
Ever since the Federation of American Scientists (FAS) reported in 2022 that RAF Lakenheath had been included in a list of nuclear weapons sites scheduled for upgrade, it has been expected that U.S. Air Force B61 bombs would eventually arrive there. The base had hosted U.S. nuclear weapons previously, and has the necessary Weapons Storage and Security System (WS3) vaults to accommodate them, but the vaults had been emptied by 2008.
On Jul. 17, 2025, aviation enthusiasts monitored the flight of C-17A Globemaster III 08-8200 across the Atlantic. Using the callsign Reach 4574 – it is unconfirmed, but suspected that four digit C-17 callsigns can refer to high priority missions – the aircraft made the unusual step of refueling in mid air off the U.S. East Coast before proceeding across the Atlantic. This arrangement is usually only considered for priority missions, with regular movements – even those noted travelling overseas during the recent situation with Iran – often making stopovers should they require fuel.
Reach 4574 departed from Kirtland Air Force Base, near Albuquerque in New Mexico. Kirtland is home to the Air Force Nuclear Weapons Center (AFNWC), which the U.S. Air Force says “synchronizes all aspects of nuclear materiel management on behalf of the AFMC commander in direct support of Air Force Global Strike Command”.
USAF C-17A #RCH4574 is inbound to RAF Lakenheath from Kirtland AFB on a nuclear airlift mission (PNAF).
08-8200 / #AE2FAC pic.twitter.com/ktJJhdBJZH
— EISNspotter 🇮🇪 (@EISNspotter) July 17, 2025
The C-17 itself hails from Joint Base Lewis–McChord, Washington. This is notable because McChord hosts the 62nd Airlift Wing, the sole unit in the U.S. Air Force cleared for routine Prime Nuclear Airlift Force (PNAF) missions.
The aircraft arrived at RAF Lakenheath just before 1200 UTC on Jul. 17. While the UK is a regular stopover point for transport aircraft heading further overseas, the routine locations for a fuel or rest stop would be RAF Mildenhall or Prestwick Airport. RAF Lakenheath, rather than a transport hub, is dedicated to the operation of F-15E Strike Eagles and F-35A Lightning IIs under the 48th Fighter Wing (48FW).
At Lakenheath, a NOTAM (Notice to Aviation (official UK terminology), or Notice to Airmen) active for Jul. 17 and Jul. 18 places a total restriction on all overflights of the Lakenheath Air Traffic Zone (ATZ) below 2000 feet. The ATZ encompasses a circle around the base with a radius of 2.5 nautical miles. An additional NOTAM, valid until Jul. 26, restricts the airfield to pre-approved movements only with no transient traffic permitted. Other notices relating to the temporary closure or usage restrictions of certain taxiways and parking areas may also be related.
The operation of this flight – including the callsign, and the use of tankers – matches those previously monitored and suspected as PNAF missions. These have been noted travelling to bases in Europe where B61s are already known to be located.
RCH3241 (C-17) about to AR with SKATR23 fit (KC-46) on the AR20 over Nova Scotia. RCH3241 departed Albuquerque, NM and is a McChord AFB 62nd AW C-17. This is the only wing in the USAF tasked with Prime Nuclear Airlift Force (PNAF) missions hence air refuel vs a stopover.… pic.twitter.com/9w0riaBRDF
— Thenewarea51 (@thenewarea51) June 13, 2023
KC-135R #LAGR72 out of RAF Mildenhall is conducting aerial refuelling with ☢️ C-17A #RCH3264 which is en route to Kirtland AFB from Büchel AB.
The 62nd Airlift Wing serves as the Prime Nuclear Airlift Force (PNAF), the only wing tasked with transporting nuclear weapons. pic.twitter.com/pIjH6vPYWG
— EISNspotter 🇮🇪 (@EISNspotter) May 28, 2024
Additional information on the return of nuclear weapons to Lakenheath, including contract notices, appeared at the beginning of 2025. According to Hans Kristensen of FAS, some of the terminology was modified after the fact to remove references related to nuclear weapons.
In our report on return of nuke mission to Lakenheath base, @elianajjohns and I show USAF quietly removed nuke language from contract document after it was reported. https://t.co/Zag3Spssc3
Previously they also altered budget document to hide nuke return. https://t.co/sZKIIpZjUM pic.twitter.com/YMXuWh2Psd
— Hans Kristensen (also on Bluesky) (@nukestrat) February 27, 2025
These reports led to the topic being picked up by UK mainstream media, including the BBC, which spawned protests by anti-nuclear campaign groups outside RAF Lakenheath.
The latest iteration of the ‘general use’ B61 variant is the B61-12, which The Aviationist has previously covered extensively. The B61-12 adds a guidance package to the existing B61 design as well as modernised safety and security features. Both the F-35s and F-15Es of 48FW would be capable of delivering these weapons.
Additionally, the UK itself is now procuring a limited number of F-35As to support F-35B training as well as contribute to the NATO nuclear force. Whether these aircraft are due to be allocated to deliver B61s stationed at Lakenheath, or if B61s will be stationed at another site in the UK (likely RAF Marham) remains to be seen.
Interestingly, the timing of this flight is also likely to attract less interest than normal from Lakenheath’s strong contingent of planespotters, as many will be otherwise engaged attending the arrivals days for the Royal International Air Tattoo at RAF Fairford. F-22s passing through the base have also very recently departed back to the United States following a rapid deployment to CENTCOM.
It’s impossible to know whether these events played any role in the scheduling of the mission, but it would not be the first time that the U.S. Air Force has adjusted some practices based on the predicted behavior of aviation enthusiasts.
Comments regarding the forward deployment of nuclear weapons are extremely rare, and what we do know of them has largely come from open source investigations, or has taken advantage of a number of improper operational security practices by U.S. forces. As such, we will likely never receive complete confirmation that this flight delivered B61s to the UK base.
