The United States Air Force is confronting significant challenges in maintaining and modernizing its strategic mobility and aerial refueling fleets, critical assets for global power projection. Recent testimony from Air Force Chief of Staff Gen. Kenneth S. Wilsbach to lawmakers highlighted a sharp decline in the mission capable rate of the service’s largest airlifter, the C-5 Galaxy, among other pressing issues affecting the aging fleet.
On April 30, Gen. Wilsbach reported that the C-5 Galaxy currently boasts a mission capable rate of 37 percent. This figure represents a considerable decrease from the 49 percent reported in fiscal year 2024, the last period for which the Air Force publicly released such data. An aircraft is considered “mission capable” when it can perform at least one of its designated core missions, serving as a key metric for fleet availability and readiness.
Gen. Wilsbach attributed the C-5’s declining readiness to a shortfall in spare parts and maintenance capacity. To address this, the Air Force has requested $24.7 billion in its fiscal year 2027 budget for aircraft sustainment. This funding, he explained, is intended to procure necessary parts and support maintenance activities to improve the operational availability of the fleet. Additionally, the budget request includes over $4 billion for the Working Capital Fund, specifically designated for acquiring critical spare parts needed for the repair and maintenance of C-5s, C-17s, and other aircraft following a period of high operational tempo, referred to as “Operation Epic Fury.” The objective is to refurbish these aircraft, extending their operational lifetimes. Gen. Wilsbach emphasized this as a strategy of “sustaining” the mobility force rather than managing its “decline.”
During the congressional hearing, committee members, including Rep. Harold Rogers (R-Ky.), questioned Gen. Wilsbach and Air Force Secretary Troy E. Meink on the service’s strategy for modernizing its mobility and tanker fleets. Rep. Rogers specifically inquired about the status of the Next Generation Airlifter (NGAL) program, asking whether the Air Force was actively replacing the C-5 and C-17 Globemaster III or merely overseeing the gradual reduction of a vital capability.
Secretary Meink responded by stating that the Air Force has concluded its analysis on the requirements for the next-generation system. He indicated that the C-5s are projected to remain in service through 2040, after which the Air Force intends to prioritize their replacement. The replacement of the C-17s, which Secretary Meink noted are currently in “very good condition,” would follow the C-5s. The unique capabilities of the C-5 Galaxy were underscored by Air Mobility Command interim boss Lt. Gen. Rebecca J. Sonkiss in February, who stated that “there is no other aircraft that can do what the C-5 does.” She further stressed that establishing a clear pathway for replacing both the Galaxy and C-17 fleets with the NGAL program would be “key to the readiness for the joint force.”
The modernization discussion also extended to the Air Force’s tanker fleet, which has faced its own set of challenges, particularly concerning battlefield connectivity. Responding to a question from Rep. Chuck Fleischmann (R-Tenn.), Gen. Wilsbach confirmed that the fiscal year 2027 budget proposal allocates $105 million for upgrading the battlefield connectivity of the tanker force. This investment aims to provide tankers with a data link network comparable to those found in modern fighter aircraft.
Lt. Gen. Sonkiss has previously identified modernized connectivity as a significant deficiency within the mobility and tanker fleets, remarking that the Air Force had been “woefully negligent… way too long” in investing in this area. While much of the public discourse on tanker modernization has centered on the proposed Next Generation Air Refueling System (NGAS), Sonkiss has also advocated for enhancing the survivability of existing tanker aircraft. She clarified that improved survivability begins with enhanced connectivity, enabling greater battlespace awareness.
Rep. Fleischmann also pressed the Air Force on its capacity to sustain tanker operations in a potential prolonged conflict in the Pacific region. A congressional mandate outlined in the fiscal year 2026 National Defense Authorization Act (NDAA) stipulates that the Air Force must possess 478 tankers by fiscal year 2027, with that number increasing to 502 by the start of fiscal year 2029. As of April 2027, official documents indicate the Air Force’s current tanker fleet stands at approximately 475 aircraft, comprising 370 KC-135 Stratotankers and 105 KC-46 Pegasus refuelers.
Gen. Wilsbach assured the committee that the Air Force expects to meet the mandated target of 478 tankers for the current fiscal year. He further stated that the service is actively working, through the current budget and anticipated future allocations, to achieve the 502-tanker goal. The Air Force’s budget request for fiscal year 2027 includes $3.9 billion for the procurement of 15 new KC-46s. Additionally, the service anticipates receiving 20 Pegasus aircraft in 2027 as part of its existing contract with Boeing, contributing to the expansion and modernization of its aerial refueling capabilities.
Why This Matters
The operational readiness and modernization of the U.S. Air Force’s mobility and tanker fleets are foundational to the nation’s defense posture and its ability to project power globally. Strategic airlift aircraft, such as the C-5 Galaxy and C-17 Globemaster III, are indispensable for rapidly deploying troops, equipment, and humanitarian aid across vast distances, enabling the U.S. to respond effectively to crises anywhere in the world. Their declining mission capable rates directly impact the speed and scale of these deployments, potentially delaying critical responses and increasing operational risks.
Similarly, the aerial refueling fleet, comprised primarily of KC-135s and KC-46s, is the lifeblood of modern air operations. These tankers extend the range and endurance of fighter jets, bombers, and surveillance aircraft, allowing them to operate in distant theaters without needing to land. Without a robust and capable tanker fleet, the U.S. military’s reach would be significantly curtailed, hindering its capacity for sustained air superiority, long-range strikes, and intelligence gathering, particularly in vast operational areas like the Indo-Pacific. The congressional mandate for increased tanker numbers underscores this strategic imperative amidst growing global challenges.
The Air Force’s substantial budget requests for sustainment and modernization — billions of dollars for parts, maintenance, new aircraft, and enhanced connectivity — represent a significant investment of taxpayer funds. These expenditures are deemed crucial for preventing the “decline” of vital capabilities and ensuring the armed forces remain prepared for future conflicts, particularly against peer adversaries. Delays in modernization or inadequate sustainment funding could result in higher long-term costs, a less effective military, and increased risks to national security. The ability to maintain and upgrade these fleets directly influences the U.S.’s credibility as a global security partner and its capacity to deter aggression and respond decisively when necessary.