TransDigm makes the small, highly specialized parts that keep commercial and military aircraft flying. Think pumps, valves, seatbelts, cockpit security systems, ignition components, and cargo loaders. What makes the business unusual is that roughly 90% of its products are proprietary, meaning TransDigm is often the only company allowed to make them. Once a part is designed into a specific aircraft, it stays there for the life of that plane, which can be 25 to 30 years. About 55% of revenue comes from replacement parts sold after planes are already in service, and 45% comes from selling parts to aircraft manufacturers building new planes. The diagram below traces where the money goes.
Five years of financials tell a clear story of expansion. Revenue climbed from $4.8 billion in 2021 to $8.8 billion in 2025. Gross margin moved in the same direction, rising from 52.4% to 60.1% over that same period. Free cash flow grew from $0.8 billion to $1.8 billion. These numbers move together in a way that suggests the business is not just getting bigger but also getting more efficient at turning sales into cash.
Gross margin above 60% is rare in manufacturing. It reflects the pricing power that comes from making parts no one else is certified to make. When an airline needs a specific valve or connector for a specific plane, there is often only one place to get it. That dynamic shows up directly in the numbers.
The other side of that story is debt. TransDigm carries a large amount of borrowings, and that number has grown sharply. Net debt rose from $14.6 billion in 2021 to $26.4 billion in 2025. A significant portion of the new debt in 2025 was raised specifically to fund a special cash dividend of $90.00 per share, paid out in September 2025. The company also paid a $75.00 per share special dividend in October 2024. TransDigm has a pattern of using borrowed money to return cash to shareholders, which is a deliberate choice but one that leaves the balance sheet carrying significant obligations.
Interest expense tells the same story. TransDigm paid $1.572 billion in net interest costs in fiscal 2025, up from $1.286 billion the year before. The weighted average interest rate on total borrowings was 6.3%. With $11.1 billion in variable-rate term loans tied to a benchmark called Term SOFR, any future rise in interest rates directly increases what the company owes each quarter. The company has hedged a portion of this exposure, and states that approximately 75% of gross debt is fixed rate, but the variable portion remains a live risk.
Beyond debt, there are other risks worth naming specifically. The top ten customers account for about 40% of total sales. Boeing and Airbus are among the companies whose production rates shape how much TransDigm sells to aircraft manufacturers. Commercial OEM sales actually declined in fiscal 2025 compared to fiscal 2024 because Boeing and Airbus production rates remain below pre-pandemic levels. Some contracts are signed at fixed prices, which means if the cost of materials or labor rises, the margin on those deals shrinks and TransDigm absorbs the difference.
There is also a structural question sitting on the balance sheet. TransDigm carries $10.6 billion in goodwill, which is 46% of total assets, and $3.5 billion in other intangible assets. These figures are the accounting record of premiums paid for past acquisitions. If those acquired businesses do not perform as expected, accounting rules require the company to write down those values, which would reduce reported assets and income by billions of dollars in a single period.
This brings the story back to its central tension. TransDigm's high margins exist precisely because it makes parts no competitor is certified to make, and because it prices those parts to reflect that position. The defense market, which represents 35% to 40% of annual sales, is also the market where that pricing has attracted the most government attention. So far the company has continued operating without a fundamental change to its model, but the scrutiny has not gone away.