The US F-35 Lightning II is the most advanced fighter in the world; however, its combat radius is approximately 500–700 nautical miles (575–800+ miles) on internal fuel, which is often viewed as a limitation for long-range operations, especially in the Indo-Pacific.
This means that when operating from aircraft carriers, they must rely more on non-stealthy air refueling tankers and/or operate much closer to their targets, which puts the carriers in harm’s way due to China’s vast A2/D2 arsenal of anti-ship ballistic missiles.
It is an issue that the US will continue to struggle with in the foreseeable future.
Geography In The Indo-Pacific Is A Significant Factor:
The F-35’s short legs are not as big a factor in Europe and the Middle East, where the air missions that the Lightning II would be tasked with are much shorter.
Flying missions in the vast Indo-Pacific are much different. The ocean is vast, with few bases that fighters can land on or refuel. The mission legs are much, much longer, and then there are the defenses that China has.
China’s missiles can reach out to 2,200 nautical miles, exposing targets well within their range. And while the planned F/A-XX reportedly has a range of 1,000+ nautical miles, it would still place the carriers within range of enemy missiles.
And loitering refueling tankers would be prime targets for the Chinese J-20 fifth-generation fighters.
F-35I Adir. Image: Creative Commons.
The US Is Working On Some Fixes For The Issue:
The Pentagon is working on the Engine Core Upgrade (ECU) for the Pratt & Whitney F135 engine, designed to improve thermal management and increase fuel efficiency, addressing both power limitations and range, though these are not expected until the late 2020s or early 2030s.
Boeing’s website says the MQ-25 Stingray “is the U.S. Navy’s first operational, carrier-based unmanned aircraft. Built to operate from aircraft carriers, its primary mission is unmanned aerial refueling to extend the range, endurance, and flexibility of the carrier air wing.”
The MQ-25A combines aerial refueling with a stealthy profile and can carry a pair of anti-ship missiles.
External Fuel Tanks Have Pros And Cons:
The US Air Force’s F-35 is undergoing upgrades to increase its combat range, primarily through the integration of external fuel tanks. External tanks are both a blessing and a curse.
A U.S. Air Force KC-135 Stratotanker aircraft flies above a U.S. Air Force F-35A Lightning II aircraft during Operation Epic Fury in the U.S. Central Command area of responsibility April 5, 2026. (U.S. Air Force photo)
While they certainly increase the aircraft’s range, they degrade the F-35’s stealth and increase drag. And if external tanks are jettisoned, the remaining mounting hardware will also affect stealth
This Air Force initiative is part of the ongoing Block 4 modernization effort and a direct response to the Israeli Air Force’s success in extending the range of its F-35I variant.
The US wants to increase the range of its F-35 and F-22 stealth aircraft, especially if the US and China go to war, given the increased distances in the Indo-Pacific.
The Israeli F-35I Stealthy External Fuel Tanks:
Conformal fuel tanks hug the fuselage of a fighter, which produces less drag and is designed to have less negative impact on the fighter’s stealth. Israel’s airstrikes against Iran last June reportedly had the F-35I Adir fighters flying to Iran and back without needing in-flight refueling.
Israel’s F-35Is flew over Turkey, Jordan, Syria, and Iraq without being detected, the Jewish News Syndicate reported.
During some of the 1,500 sorties that F-35I aircraft flew over Iran, they utilized two types of fuel tanks: a 425-gallon external fuel tank made by Israel’s Elbit Systems, which is suspended under the wings and dropped before entering Iranian territory; and an 800-gallon conformal tank, developed in collaboration with Israel Aerospace Industries and Lockheed Martin.
The new F-35 Lightning II stands on display at the First Aircraft Arrival ceremony on Nov. 2, 2024, at Naval Air Station Joint Reserve Base Fort Worth, Texas. The delivery of the F-35 ushered in a new era of modern-day warfighting for the U.S. Air Force. (U.S. Air Force photo by Staff Sgt. Richard Moser)
The Israeli Air Force’s F-35I, known as “Adir”, has already demonstrated the effectiveness of external fuel tanks and conformal fuel tanks in extending the aircraft’s range. Their experience in successfully striking targets in Iran, without (in some cases) needing aerial refueling, highlighted the potential of this upgrade for the broader F-35 fleet.
Incorporating External Fuel Tanks:
The U.S. Air Force is actively exploring the integration of external fuel tanks on the F-35A to significantly extend its combat radius. This would allow for longer-range missions without relying on tanker support, enhancing operational flexibility and survivability.
Seven F-35 Lightning II aircraft wait to take off for a U.S. Air Force Weapons School training mission at Nellis Air Force Base, Nevada, Jan. 31, 2024. The U.S. Air Force Weapons School teaches graduate-level instructor courses that provide advanced training in weapons and tactics employment to officers and enlisted specialists of the combat and mobility air forces. (U.S. Air Force photo by William R. Lewis)
Alex Hollings from Air Power and Sandboxx wrote, “The F-35A can carry 18,498 pounds of fuel internally, which gives it an already respectable combat radius of some 670 nautical miles. The addition of two 600-gallon stealthy drop tanks would provide approximately another 8,000 pounds of fuel to the F-35A and stretch its combat radius out to more than 1,100 miles with a combat load.”
The expanded range capabilities are seen as crucial for addressing current and future operational needs, particularly in scenarios where aerial refueling is neither feasible nor desirable.
F-35 Block 4 Modernization:
The F-35 Block 4 upgrade is a significant modernization program for all three F-35 variants, focusing on a new radar, enhanced sensors, expanded weapons capacity, and improved electronic warfare systems.
Block 4 is “really going to be about enhancing the sensor upgrades, the sensor fusion, and also bringing the new weapons” to the jet, Chauncy McIntosh, Vice President and general manager of the F-35 program, said.
During an interview with Air & Space Forces Magazine, McIntosh said the threat is driving recurrent revisions to the top priorities for Block 4 and later (Block 5) upgrades.
“We have to continue to advance this airplane regarding where that threat is going,” he said. “And so we’ve laid out a plan and a strategy for Block 4, and what we need to do to ensure we stay ahead of that threat.”
U.S. Air Force Maj. Melanie “Mach” Kluesner, pilot for the F-35A Demonstration Team, preforms high-speed aerial maneuvers during a practice demonstration at Hill Air Force Base, Utah, Jan. 6, 2026. The team practices during their off-season to ensure that they are always sharp and ready to demonstrate the capabilities of the F-35A and the U.S. Air Force. (U.S. Air Force photo by Staff Sgt. Nicholas Rupiper)
This involves over 75 new programs and is considered the most significant evolution of F-35 capabilities to date, according to National Defense Magazine.
The integration of external fuel tanks is part of the Block 4 upgrade package.
Tech Refresh-3 (TR-3), which enables Block 4, introduces open mission systems architecture, a new integrated core processor with greater computing power, an enhanced panoramic cockpit display, a larger memory unit, and other classified capabilities.
Increased Costs Add To An Already Expensive Program:
The Fiscal Year 2026 U.S. defense budget proposes to slash purchases of new F-35s in part to provide more funding for the Block 4 effort, as well as to help sustain existing Joint Strike Fighter fleets.
Despite this, F-35 production was 190 aircraft in 2025. Our allies are sure to be keeping a sharp eye on the external fuel tank development.
While the F-35 program has faced cost increases, the need for enhanced range and operational flexibility outweighs these concerns. The potential benefits of increased range and survivability justify the investment in these upgrades.
Will The External Tanks For The F-35 Be Stealthy Enough?
The F-35’s enhanced range will likely play a significant role in future air combat scenarios, allowing for more effective power projection and a wider operational envelope.
If these external conformal fuel tanks are stealthy enough, as the ones co-produced by the Israelis and Lockheed, then the F-35s just got a much longer range, which will increase their overall effectiveness without requiring more refueling tankers.
About the Author: Steve Balestrieri
Steve Balestrieri is a National Security Columnist. He served as a US Army Special Forces NCO and Warrant Officer. In addition to writing on defense, he covers the NFL for PatsFans.com and is a member of the Pro Football Writers of America (PFWA). His work was regularly featured in many military publications.
