Investment thesis · Live

New jet engines are still causing problems, driving a historic boom in the aftermarket for parts and MRO services

Reliability issues with new-generation engines and delays in jet deliveries are forcing airlines to extend the life of older aircraft. That is turning the market for parts, MRO work and leasing into a genuine cash machine.

Published July 6, 2026 · 120-day horizon · supply and demand

Basket return

-28.2%

equal weight, since publication

The market over the same window

+0.6%

benchmark for this basket

Edge over the market

-28.8%

in percentage points

Causal chain: Shortfalls in new aircraft deliveries to the market → High failure rates on new-generation jet engines (GTF, LEAP) → Airlines keep old aircraft in service far longer → Demand surge and sharp price increases in the aftermarket → Huge parts margins for the major engine makers → Step change in work orders for independent MRO → The market for leasing, PMA parts and USM components

What this thesis rests on

Each one is a statement that has to be true. We go back to every live thesis on a schedule and check these against public sources, so each leg carries either what we found or the date we look next.

Checked every 14 days. Last review September 15, 2026, next one September 29, 2026.

Boeing and Airbus do not announce a restored narrowbody delivery schedule: Boeing 737 output stays at or below 42 jets per month with no FAA approval of a higher rate before 3 November 2026.
regulatory · Challenged

A source challenges this · August 29, 2026

Boeing's Q2 2026 results release (28 July 2026) states the 737 program "began transitioning production to 47 per month rate in the quarter" and "activated low-rate initial production on the 737 North Line in July", above the 42/month ceiling the claim requires through 3 November 2026.
See the source ↗
RTX discloses an average of more than 300 GTF-powered A320neo-family aircraft on ground in each quarterly report filed during the 120-day horizon, with no powder-metal inspection completion declared.
operational · Open
Checked September 15, 2026, nothing published either way
Willis Lease Finance reports lease rent revenue up at least 15% year over year in the two quarterly filings after publication, showing spare-engine lease rates have not broken.
financial · Challenged

A source challenges this · August 29, 2026

Willis Lease Q2 2026 results (4 August 2026): lease rent revenue $77.1m vs $72.3m, up $4.9m or 6.7% year over year, against the 15% the claim requires in each of the two post-publication quarters.
See the source ↗
Safran reports civil aftermarket revenue growth of at least 10% year over year in its H1 2026 results, carried by CFM56 spare parts and shop visits rather than new LEAP deliveries.
financial · Supported

A source confirms this · August 29, 2026

Safran H1 2026 results (28 July 2026): civil engine spare parts revenue up 27.9% in dollar terms, driven notably by favourable workscope mix on CFM56, and services up 40.4%. CFM56 new-engine deliveries fell to 22 from 26 units, so growth came from aftermarket, not new deliveries.
See the source ↗
Heico keeps its FAA PMA approvals with no suspension or adverse airworthiness action disclosed, and reports Flight Support Group net sales growth of at least 10% year over year in the quarter after publication.
regulatory · Supported

A source confirms this · August 29, 2026

HEICO fiscal Q3 2026 results (quarter ended 31 July 2026, released 26 August 2026): Flight Support Group net sales up 18% to a record $947.8m from $802.7m, organic growth 12%. No suspension or adverse airworthiness action against its FAA PMA approvals disclosed in the release.
See the source ↗

The setup: two market anomalies hitting at once

Commercial aviation is currently dealing with two powerful supply shocks. First, Boeing and Airbus are permanently unable to deliver enough new narrowbodies to the market. MAX output is being choked by tightened regulatory scrutiny, while A320neo supply is held back by bottlenecks at subcontractors. Second, the newest powerplants have turned out to be highly temperamental. Faulty powder metallurgy forced Pratt & Whitney into a global inspection campaign on GTF engines, grounding hundreds of Airbus jets in the process. At the same time, LEAP engines (from the CFM joint venture) are holding up badly in harsh, hot-and-high operating conditions. The need for frequent shop visits radically shortens their time on wing. The result: the industry has nowhere to source new aircraft, and on top of that it cannot fully trust the ones it already owns.

Companies in the basket

SAF · Safran MTX · MTU Aero Engines WLFC · Willis Lease Finance HEI · Heico

This thesis, over time

What has happened since publication. Every entry is computed as of its own date, from price history.

September 15, 2026

Review on day 71: nothing moved

We went back to this thesis on day 71 of 120 and checked each of its 5 assumptions against public sources. No news either way: 5. The equal-weight basket stands at -29.2% since publication day. The benchmark (.INX) returned +1.1% over the same window, so the basket trails its market by 30.3 percentage points. 49 days remain until the verdict.

September 4, 2026

Day 60 of 120: basket -25.8%

The thesis is halfway to its verdict. The equal-weight basket stands at -25.8% since publication day. The benchmark (S&P 500) returned +2.8% over the same window, so the basket trails its market by 28.6 percentage points. The strongest contributor is SAF (-8.0%), the weakest is WLFC (-75.5%). 60 days remain until the verdict.

August 29, 2026

Review: 2 of 5 assumptions broken

We went back to this thesis on day 54 of 120 and checked each of its 5 assumptions against public sources. Broken by the sources: 2. Confirmed by the sources: 2. No news either way: 1. The equal-weight basket stands at -23.4% since publication day. The benchmark (.INX) returned +2.3% over the same window, so the basket trails its market by 25.7 percentage points. 66 days remain until the verdict.

August 5, 2026

Day 30 of 120: basket -17.4%

The first quarter of the horizon is behind this thesis. The equal-weight basket stands at -17.4% since publication day. The benchmark (S&P 500) returned +2.5% over the same window, so the basket trails its market by 19.8 percentage points. The strongest contributor is HEI (+1.8%), the weakest is WLFC (-69.8%). 90 days remain until the verdict.

July 21, 2026

Basket fell below -20% since publication

This basket is at -24.5% since publication, 15 days after the thesis was posted. The benchmark (S&P 500) returned -0.4% over the same window, so the basket trails its market by 24.2 percentage points. The strongest contributor is HEI (-5.5%), the weakest is WLFC (-70.4%). This is not a change of status: the horizon keeps running and the verdict only lands once it expires.

July 20, 2026

Basket fell below -10% since publication

This basket is at -11.0% since publication, 14 days after the thesis was posted. The benchmark (S&P 500) returned -1.3% over the same window, so the basket trails its market by 9.7 percentage points. The strongest contributor is HEI (-6.0%), the weakest is WLFC (-15.9%). This is not a change of status: the horizon keeps running and the verdict only lands once it expires.

Open the interactive thesis

Interactive causal map, the basket charted against its market, and the full timeline.

Open in Invesaro →

This is analysis, not investment advice and not a recommendation to buy or sell anything. We publish it and track it in public, mistakes included. Any decision is yours and yours alone.