F135: Sole Source on Every F-35Wide moat

RTX (RTX) — moat facet

The F135 is the only engine for every F-35, so Pratt & Whitney's military business has no competitor for production or for decades of sustainment.

Pratt & Whitney has a franchise no commercial engine has: the F135 is the sole-source engine for all three variants of the F-351. RTX's announcement of the next Pratt & Whitney president credited her with securing the company's "sole source propulsion position on the F-35"2.

Pratt & Whitney defence bookings, 2025 ($bn)2.9F135 production2.4F135 sustainment3.7Other militaryRTX Form 10-K FY2025; total about 9.0bn, other by difference
The F135 was most of the year's military orders.

Sole source means there is no competition for the engine or for its sustainment, for as long as the aircraft flies. The customer is the U.S. government and its allies, and the airframer is Lockheed Martin, which P&W supplies.

The money is large and recurring. Pratt & Whitney booked about $9 billion of defence orders in 2025, including $2.9 billion of F135 production and $2.4 billion of F135 sustainment3. In the second quarter of 2026 military engine sales rose 23%, "driven by higher F135 volume"4, helped by the timing of the Lot 18 award.

The F135 also lends Pratt & Whitney something the commercial side lacks: government-funded engineering. Customer-funded research and development across RTX was $4,886 million in 2025, against $2,807 million funded by the company5.

Sustainment is the underrated part. Production ends when the last jet is built; sustainment runs for decades, and it is contracted with the same monopoly supplier.

The customer also pays for much of the engineering. Of RTX's research spending in 2025, $4,886 million was funded by customers, against $2,807 million funded by the company6. On a sole-source programme that is an unusual advantage: the government pays to keep its only supplier technically ahead.

The succession choice shows where the company sees value: the head of Military Engines becomes president of Pratt & Whitney on 1 January 20277. Watch F135 sustainment awards against production awards; when sustainment overtakes production, the programme will have become an annuity.

Moat trajectory: Widening

Military engine sales +23% in Q2 2026 on F135 volume.

The number that tests this moat
Reported
Pratt & Whitney military sales growth, latest quarter
+23% (Q2 2026)

The F135 franchise in motion; flat or falling military sales in a rising defence budget would mean the programme has peaked.

Source: RTX Q2 2026 earnings call transcript ↗
⚠ Threats to the moat
⚠ THREAT 01
One Aircraft, One Customer
The F135 has no competitor, but it has one aircraft and one lead customer, and each annual production lot moves Pratt & Whitney's numbers.
References
  1. ReportedPratt & Whitney has a franchise no commercial engine has: the F135 is the sole-source engine for all three variants of the F-35.
    RTX Form 10-K for fiscal 2025 - Item 1 business: the three segments and their products, the GTF family powering more than 2,600 aircraft for over 90 operators, the F135 as sole-source engine on all F-35 variants, GTF Advantage certification, the IAE collaboration shares, employees (about 180,000 in 52 countries, 69% in the U.S.) and the divested businesses. — FY2025 · publ. 6 February 2026 · source ↗
  2. ReportedRTX's announcement of the next Pratt & Whitney president credited her with securing the company's "sole source propulsion position on the F-35".
    RTX press release of 15 September 2026, Form 8-K exhibit 99.1 - Pratt & Whitney president Shane Eddy to retire; Jill Albertelli, president of Military Engines, to succeed him on 1 January 2027. — September 2026 · publ. 15 September 2026 · source ↗
  3. ReportedPratt & Whitney booked about $9 billion of defence orders in 2025, including $2.9 billion of F135 production and $2.4 billion of F135 sustainment.
    RTX Form 10-K for fiscal 2025 - customers and backlog: sales to the U.S. government (38%, 40%, 46% of net sales in 2025-2023), Airbus (about 14%, 14%, 17% before discounts and incentives; 29%, 31%, 48% of Pratt & Whitney sales), Boeing and Airbus at 16% of Collins sales, international sales of 47%, and total, commercial and defence backlog with remaining performance obligations. — FY2023-FY2025 · publ. 6 February 2026 · source ↗
  4. ReportedIn the second quarter of 2026 military engine sales rose 23%, "driven by higher F135 volume", helped by the timing of the Lot 18 award.
    RTX second-quarter 2026 earnings call transcript (The Motley Fool) - Raytheon bookings and book-to-bill, GTF aircraft-on-ground and MRO output, munitions output, framework agreements, the defence budget request, GTF Advantage, Collins margin plans and segment outlook - defence: Raytheon bookings, book-to-bill and backlog, munitions output, framework agreements and the budget request. — Q2 2026 · publ. 24 July 2026 · source ↗
  5. ReportedCustomer-funded research and development across RTX was $4,886 million in 2025, against $2,807 million funded by the company.
    RTX Form 10-K for fiscal 2025 - consolidated financial statements and notes: income statement, cash flow, dividends and repurchases, long-term debt of $37,700 million, goodwill by segment, pension income, the 2024 resolution of certain legal matters, the Raytheon contract termination and the accelerated share repurchase. — FY2023-FY2025 · publ. 6 February 2026 · source ↗
  6. ReportedOf RTX's research spending in 2025, $4,886 million was funded by customers, against $2,807 million funded by the company.
    RTX Form 10-K for fiscal 2025 - consolidated financial statements and notes: income statement, cash flow, dividends and repurchases, long-term debt of $37,700 million, goodwill by segment, pension income, the 2024 resolution of certain legal matters, the Raytheon contract termination and the accelerated share repurchase. — FY2023-FY2025 · publ. 6 February 2026 · source ↗
  7. ReportedThe succession choice shows where the company sees value: the head of Military Engines becomes president of Pratt & Whitney on 1 January 2027.
    RTX press release of 15 September 2026, Form 8-K exhibit 99.1 - Pratt & Whitney president Shane Eddy to retire; Jill Albertelli, president of Military Engines, to succeed him on 1 January 2027. — September 2026 · publ. 15 September 2026 · source ↗
Sources
Generated September 28, 2026