AIR vs TDG: Which Is the Better Buy in 2026?

Same yardstick, side by side (as of August 2026). Valuation lined up like this is most meaningful for two names in the same corner of the market, which these are. Figures are approximate; verify before investing.

Reading it: AIR is the cheaper of the two on forward earnings, but cheaper is not the same as better. Pair the valuation with growth (how far the forward P/E sits below the trailing P/E) and risk (beta) before you decide.

The metrics above tell you which is the marginally better business. The bigger risk for most people is not picking the slightly worse stock, it is over-concentrating. AIR and TDG share themes, so owning both, or adding either to what you already hold, can quietly push a large share of your portfolio into one bet.

This is the part a generic comparison page cannot answer, because it depends on what you own. Connect your brokerage and Walnut shows your real, combined AIR and TDG exposure, flags overlap with your existing positions, and tells you if adding one would tip you past a concentration you are comfortable with, read-only by default, with your login staying at your broker. Walnut is not an investment adviser.

AAR Corp is a leading independent provider of aviation services to commercial airlines, government and defense operators, MRO shops, and OEMs. It operates across four segments: Parts Supply (selling and leasing used serviceable material and new parts), Repair & Engineering (airframe and component maintenance), Integrated Solutions (including the Trax cloud MRO software platform and government logistics programs), and Expeditionary Services (mobility and pallet products). The business is squarely an aftermarket story: it makes money keeping existing aircraft flying rather than building new ones, which gives it exposure to global flight hours, fleet age, and defense sustainment budgets.

Full AIR guide

TransDigm Group designs and manufactures highly engineered aerospace components used on commercial and military aircraft. Its business model is distinctive: it focuses on proprietary, sole-source parts (things like pumps, valves, actuators, ignition systems, cockpit controls, and specialized fasteners) where TransDigm is often the only approved supplier for a given aircraft. A large share of revenue comes from the aftermarket, selling replacement parts and spares over the decades-long service life of an aircraft, which carries very high margins and recurring demand. TransDigm grows through a disciplined acquisition strategy, buying niche aerospace-parts makers with similar proprietary, sole-source characteristics and then applying its playbook of value-based pricing and cost discipline. The company is known for a private-equity-style approach to capital allocation, high leverage, and large special dividends. Headquartered in Cleveland, Ohio, it serves commercial airlines, business jets, and defense customers worldwide.

Full TDG guide

Both fit overlapping themes, but they are not interchangeable. The useful comparison is which set of drivers and risks you want exposure to.

• AIR drivers: Aging global fleet and record flight activity; Shift toward higher-value repair and software.
• TDG drivers: High-margin proprietary aftermarket; Acquisition-driven growth.

A faster-growing, richer-valued name usually swings harder, so it suits a longer horizon and a higher tolerance for volatility; a steadier, more cash-generative business suits a more conservative or income-minded investor. The honest test is which set of risks you could hold through a drawdown: AIR is cyclical: a downturn in air travel, airline capacity cuts, or a recession would reduce flight hours and maintenance demand. For TDG, transDigm carries very high debt, a deliberate part of its model, which raises interest costs and financial risk if cash flow weakens or rates stay elevated.

Pick AIR if you believe its drivers more; TDG if you believe its. Many investors hold both, but since they share themes, that is a concentrated bet, not diversification. Decide deliberately and check overlap. For the full detail, see the AIR and TDG guides.

AIR. AAR posted accelerating growth through fiscal 2026, with quarterly sales climbing from roughly $740M to about $845M and adjusted EBITDA and EPS growing at double-digit rates. Management guided full-year fiscal 2026 to roughly 19% total sales growth and about 12% organic growth. The roughly 31x earnings multiple reflects those expectations, so the valuation embeds continued execution.

TDG. TransDigm trades at a premium valuation justified by best-in-class margins, a wide sole-source moat, and a long record of compounding through acquisitions. The qualitative profile is a high-quality, highly levered aerospace compounder. The premium multiple and high leverage mean the stock is sensitive to air-traffic cycles, acquisition pace, and any erosion of pricing power.

Headline figures (approximate, JULY 2026): AIR shows revenue (ttm) ~$3.1B, q3 fy2026 sales ~$845M (up ~25% YoY), q3 fy2026 adj. eps ~$1.25 (up ~26% YoY), market cap ~$5.6B; TDG shows revenue (ttm) ~$8 to 9 billion, ebitda margin ~50%, among the highest in aerospace, aftermarket revenue share roughly half of total revenue, net leverage high, by design (around 5x EBITDA).

AIR and TDG are related but distinct: same themes, different businesses and risks. Neither wins in the abstract; the right pick is whichever thesis you actually believe, sized so you are not over-concentrated in one theme. Walnut can show your combined AIR and TDG exposure against your real portfolio. It is not an investment adviser.