The Alternate Engine is a Settled Issue

There should be no third bite at the taxpayers’ money for the twice-killed alternate engine for the F-35 Joint Strike Fighter (JSF).  In 2011, following years of opposition from multiple presidential administrations and the Department of Defense (DOD), along with a coalition of taxpayer organizations, the first attempt to provide an alternate engine for the JSF was shuttered, but not before members of Congress had added 13 earmarks costing $1.5 billion.

Then, in 2023, new JSF capabilities led the DOD to explore options for a more powerful engine.  As Citizens Against Government Waste suggested, the DOD ultimately chose to cost-effectively upgrade the existing engine through the Engine Core Upgrade program (ECU) instead of funding a second engine through the Adaptive Engine Transition Program (AETP).

Like the first go-round, many of the same arguments against the alternate engine still applied.  The second effort to build a second engine was opposed by the DOD, the White House, and taxpayer groups, and only supported by a handful of legislators motivated by parochial concerns.

In a April 27, 2023, Senate Defense Appropriations Subcommittee hearing, then-Air Force Secretary Frank Kendall stated that the AETP would have required, “a large upfront cost associated with engineering, manufacturing and development.”  The Air Force estimated that AETP development costs would have been nearly $6.7 billion, which was 279 percent more than the $2.4 billion development cost for the ECU projected by Pratt & Whitney, which determined that the ECU would save tens of billions of dollars in total JSF lifecycle costs by avoiding a duplicative production line and global supply chain to service two separate engines.  Secretary Kendall said that another adverse consequence of building an alternate engine would mean the Air Force alone would be forced to purchase 70 fewer JSFs.

In addition to cost, the alternate engine also failed another basic threshold:  compatibility.  The second engine would not fit in the Marine Corp’s F-35B variant, and would require substantial airframe modifications to work with in the F-35A and F-35C.

In his comments following a meeting in Qatar on May 15, 2025, President Trump speculated, among other topics, on the potential for the JSF to be upgraded with a second engine.  While defense officials have been silent on the issue, they should be cognizant that agreeing to try for the third time to build an alternate engine would be diametrically opposed to President Trump’s insistence on cutting waste, fraud, and abuse as he said several times while promoting the reconciliation bill in the House of Representatives on May 20, 2025.

Proponents of the alternate engine have cited the advantages of “competition.”  While that process often results in cost savings, to achieve that objective with an alternate engine would require two teams of engineers, duplicate sets of tooling, parts, assembly sites, repair facilities, supply chains, management systems, workforces, and every other cost of production.  It would also make the JSF program, which already suffers from a poor readiness rate, even harder to maintain and keep flying consistently.

President Trump may have made his comments in the hope that a second engine could save money and increase efficiency.  But there is more than sufficient evidence that it would not achieve that objective.  With projected lifetime operations and maintenance costs of $1.727 trillion for the JSF, trimming costs in the most expensive weapons system in history is vital.  There is no room in the picture for an unnecessary second engine.