KC-46 vs KC-135: Which Tanker Do C-17 Pilots Prefer?

Every C-17 pilot knows the drill: you’re at 25,000 feet, fuel gauges dropping, and somewhere ahead is a tanker with 150,000 pounds of JP-8 waiting to extend your mission. Whether that tanker is a KC-135 Stratotanker or the newer KC-46 Pegasus determines how that refueling will go—and every mobility pilot has opinions about which is better.

This comprehensive comparison examines both tankers from the perspective of the pilots who depend on them: the C-17 crews who spend hours forming up, plugging in, and taking gas.

The Tankers at a Glance

The KC-135: 70 Years of Getting It Done

The KC-135 Stratotanker has been refueling aircraft since Eisenhower was president. Originally designed to support the B-52 bomber fleet, it has evolved into the backbone of American air refueling capability.

What C-17 Pilots Like About the KC-135

• Predictability: Boom operators have decades of experience. They know exactly how C-17s behave during refueling.
• Direct communication: The boom operator looks directly at your aircraft and can anticipate your movements.
• Proven procedures: Every technique has been refined over millions of refueling operations.
• Availability: With nearly 400 aircraft, KC-135s are everywhere you need them.

KC-135 Limitations

• Age: Many airframes are 60+ years old. Maintenance issues can cause cancellations.
• Fuel efficiency: Four older-generation engines consume more fuel than modern alternatives.
• Receiver capacity: Limited to one receiver at a time with the boom (two with drogue adapters).
• Crew fatigue: The boom operator position is physically demanding during long missions.

The KC-46: The Controversial Newcomer

The KC-46 Pegasus was supposed to be a straightforward replacement—take a modern airframe, add refueling capability, deploy worldwide. Reality has been more complicated.

What C-17 Pilots Like About the KC-46

• Modern airframe: Based on the reliable Boeing 767, with modern engines and systems.
• Larger fuel capacity: More gas to offload means more flexibility for receivers.
• Cargo capability: Can carry passengers and pallets while performing tanker duties.
• Self-defense: Designed with survivability features for contested environments.

The Controversy: Remote Vision System Problems

The KC-46’s most significant issue has been its Remote Vision System (RVS)—the camera system that allows boom operators to control refueling from a station inside the aircraft rather than the traditional prone position looking directly at the receiver.

Problems include:

• Depth perception issues that make precise boom positioning difficult
• Image quality degradation in certain lighting conditions
• Boom strikes that have damaged receiver aircraft
• Restrictions on which aircraft can safely refuel from the KC-46

As of 2025, Boeing continues working on RVS 2.0 to address these issues. Progress has been made, but the system still doesn’t match the human eye.

The C-17 Refueling Experience: KC-135 vs KC-46

Flying Formation to the Tanker

From the C-17 cockpit, joining on either tanker is similar. You’ll:

1. Receive coordinates and rendezvous instructions
2. Navigate to the tanker track
3. Establish visual contact
4. Move to the pre-contact position

The KC-46 is notably larger than the KC-135, which can affect visual perception during the join-up. New C-17 pilots sometimes misjudge distance when first refueling from a Pegasus.

The Contact Position

This is where the differences become apparent.

With the KC-135: The boom operator is lying prone, looking through a window directly at your aircraft. They can see your control inputs, anticipate your movements, and provide direct feedback. Communication feels natural.

With the KC-46: The boom operator watches through cameras on multiple screens. The perspective is different. Some C-17 pilots report that the boom seems to react more slowly to their movements, requiring more deliberate flying.

Fuel Transfer

Once connected, both tankers deliver fuel efficiently. The KC-46’s slightly higher transfer rate (1,200 vs 1,100 gallons per minute) provides a marginal advantage during large offloads, but the difference is negligible for typical C-17 operations.

A C-17 taking 100,000 pounds of fuel will spend approximately 10-12 minutes connected to either tanker.

Disconnect and Departure

The disconnect procedure is standard for both tankers. However, KC-46 RVS issues have occasionally led to unintentional disconnects—the boom backing out when it shouldn’t. C-17 crews flying with KC-46s are briefed to expect this possibility.

Real Pilot Perspectives

We spoke with C-17 pilots about their experiences with both tankers:

“The KC-135 feels like refueling with a partner. The boom operator and I are working together. With the KC-46, it sometimes feels like flying with technology that’s still figuring itself out.” — Major, 8 years C-17 experience

“I’ve had smooth refuelings from KC-46s and rough ones from KC-135s. The tanker matters less than the crew operating it. A good boom operator makes any platform work.” — Captain, 4 years C-17 experience

“The KC-46 will be excellent once they fix the vision system. The airframe is more capable in every measurable way. We just need the boom to work as designed.” — Lieutenant Colonel, KC-46 evaluator pilot

The Future of C-17 Air Refueling

The KC-135 cannot fly forever. Despite continuous upgrades, airframes built in the 1950s and 1960s will eventually need replacement. The KC-46 was designed to be that replacement.

Timeline considerations:

• KC-135s are currently planned to serve into the 2040s
• KC-46 deliveries continue, with 179 aircraft on order
• RVS 2.0 upgrades are expected to resolve most current issues
• Next-generation tanker concepts are already being studied

For C-17 pilots, this means increasing familiarity with the KC-46 is essential. The aircraft that will extend your missions for the next 30 years is the Pegasus.

Tips for C-17 Pilots Refueling from KC-46

Based on current operational experience:

1. Fly precisely: The RVS has less tolerance for receiver movement than a human observer. Keep corrections small and smooth.
2. Communicate clearly: The boom operator’s situational awareness is more limited. Clear, concise radio calls help.
3. Expect variability: RVS performance varies with lighting. Night refueling can be particularly challenging.
4. Trust the training: KC-46 boom operators are well-trained. Give them time to work.
5. Report issues: Safety reporting helps Boeing and the Air Force identify and fix RVS problems.

The Bottom Line

Both tankers accomplish the fundamental mission: delivering fuel to thirsty aircraft. The KC-135’s decades of refinement make it a comfortable, predictable platform. The KC-46’s growing pains are real but temporary.

The best tanker is the one that shows up when you need gas. For the foreseeable future, that will be a mix of both aircraft—and C-17 crews need to be proficient with both.

Whether you’re plugging into a Vietnam-era KC-135 or a brand-new KC-46, the mission remains the same: get gas, complete the mission, bring everybody home.