The electrical guts of an aircraft — wire harnesses, in-seat power units, circuit-card assemblies, radar racks — are sold against certified part numbers, not brands, and the companies that make them almost never appear in a headline. Three of the largest American suppliers of that hardware reported June-quarter results this month, and all three reported records. Two of their stocks have roughly doubled in a year. The question is what was actually bought.

Ducommun: the arithmetic behind the margin

Ducommun, a Santa Ana, California manufacturer that builds other companies' designs — interconnects, printed circuit-board assemblies, lightning-diversion systems and contoured aluminum and titanium airframe structures — reported revenue of $224.5m, up 11.0% from a year earlier. Gross margin reached 28.0%, up 160 basis points, and operating income rose 59.4%. The company reported all-time-high remaining performance obligations of $1.2bn, quarterly bookings of $309.7m and a book-to-bill of 1.4x, with missile revenue up 68% on PAC-3, THAAD, Tomahawk and AMRAAM work.

The margin, though, has a mundane source. Management's multi-year performance-center consolidation hit its full $13m annual run rate in the quarter. On fiscal 2025 revenue of $824.8m, $13m is about 158 basis points — arithmetically almost the entire gross-margin gain. The parallel story, that engineered products have grown from 15% of revenue in 2022 to 23% today, has yet to show up as a separate contribution. And the missile narrative is not what is driving the top line: commercial aerospace revenue rose 16% to $89m, faster than defense's 7% rise to $124m.

That commercial leg is a real mechanism. The Federal Aviation Administration lifted the 737 MAX production cap in March, and Boeing has moved to 47 aircraft a month from 42, with 52 targeted for early next year; Airbus is pushing toward 75 A320-family jets a month by mid-2027. More shipsets, more content.

What the price has already taken is the harder point. A fiscal 2025 charge left trailing earnings meaningless, so gross profit is the usable lens: Ducommun trades at 12.86x trailing and 12.54x forward gross profit, against roughly 6.5x a year ago, while trailing gross profit grew 14.9%. On consensus 2026 earnings of $4.16 a share, that is 48.1x forward. L3Harris trades at 23.2x. Management unveils a successor to its VISION 2027 plan at an investor day in New York on 17 September; adjusted EBITDA margin is 17.1% against the existing 18% target.

Astronics: the record is in the small segment

Astronics, of East Aurora, New York, is not really an avionics vendor — it makes cabin and airframe electrical power, lighting and connectivity systems, plus automated test equipment for defense and semiconductor customers. Revenue rose 27.0% to $260.0m, gross margin expanded 760 basis points to 33.4%, and operating margin went from 2.3% to 15.6%. The company raised full-year guidance past $1bn for the first time on record bookings of $306m and record backlog of $780.5m.

The concentration matters. Book-to-bill was 2.78x in Test Systems, a unit that turned $0.6m of operating profit on $22.7m of sales; in the Aerospace segment tied to narrowbody build rates, it was 1.02x. About 70 basis points of the gross margin came from a one-time $2m tariff refund. Debt stands at $310.3m, roughly 1.9x consensus 2026 EBITDA, and the Lufthansa Technik patent fight continues in France and Germany even after a UK appellate court dismissed Lufthansa's damages appeal in its entirety in July. Still, at 10.24x trailing gross profit Astronics is the cheapest of the three, and its multiple rose 72% over a year in which gross profit grew 48.4% — more of that move was earned than at Ducommun.

HEICO: the aftermarket that isn't compounding

HEICO, a $50.6bn Florida group whose FAA-approved replacement parts undercut engine makers' own by 30% to 50%, grew revenue 25.3% to $1.376bn with operating margin of 25.5%. But gross margin compressed 110 basis points to 41.4%, and the parts franchise geared to airline flying grew just 2% organically — against industry traffic forecast to expand 4.9% this year. Growth came from acquisitions: four year to date, net debt at 1.74x EBITDA, and a $1.2bn senior notes offering closed in July. At 25.73x trailing gross profit versus roughly 24.6x a year ago, HEICO has not re-rated at all; its 18.3% gain was paid for in profit. Fiscal third-quarter results are due after the close on 25 August.

L3Harris is the counter-case. It beat on the quarter and raised full-year guidance to as much as $23.7bn on a $42bn backlog — and the shares fell, then kept falling. It has been in a sustained downtrend since 11 June, sits 26.8% below its 12-month high, and trades at 8.83x gross profit with a 5.4% free-cash-flow yield. Investors fixed on capital intensity: research and capital spending each up over 20%, and the missile-business listing pushed to mid-2027.

What the month actually was

None of this was a grind. Astronics' entire month was one session — a 16.7% jump on 12 August — and it has since surrendered roughly half of it, including a 5.2% drop on 18 August attributed to a broad industrials selloff rather than anything the company said. Three-quarters of Ducommun's month came in two sessions; 72% of HEICO's came in one. Only Ducommun has held an unbroken uptrend, its 50-day average above its 200-day since 24 December.

The setup

Where it stands — Two small suppliers have re-rated sharply on quarters whose margin gains have identifiable one-time components; the large-cap aftermarket compounder has not re-rated at all. Would confirm — Ducommun holding gross margin at or above 28% in the September quarter, with the consolidation program already at full run rate. Would invalidate — Astronics' Aerospace book-to-bill falling below 1.0x, or Ducommun's remaining performance obligations declining from $1.2bn. Watch next — HEICO's fiscal third quarter after the close on 25 August; Ducommun's investor day in New York on 17 September. Valuation — Ducommun at 12.86x trailing and 12.54x forward gross profit, against roughly 6.5x a year ago; Astronics 10.24x, HEICO 25.73x.