Every kilogram you remove from an aircraft saves roughly $3,000 a year in fuel. That number gets thrown around a lot in aerospace — but when you actually do the math on a fleet of 200 aircraft flying 3,000 hours a year each, the savings are real. A 50kg weight reduction across the fleet saves about $30 million annually.
Engineering plastics have been replacing metal in aerospace for decades, but the pace has accelerated in the last five years. Here's what's driving it and where the materials actually go.
What's pushing plastics into more aircraft
Three things, mostly:
Fuel cost and emissions pressure. Lighter aircraft burn less fuel. Airlines care because fuel is their #1 or #2 operating cost. Manufacturers care because emissions regulations are tightening worldwide. A 40-70% weight reduction versus aluminum on non-structural components adds up fast.
Galvanic corrosion elimination. Carbon-fiber reinforced polymer (CFRP) airframes — now standard on the 787 and A350 — create a nasty galvanic couple with aluminum fasteners and brackets. You get corrosion at every joint unless you isolate the metals. PEEK and PEI fasteners solve this at the design level because they're electrically insulating. No galvanic couple, no corrosion.
Simplified manufacturing. A machined or injection-molded plastic bracket comes out of the tool finished. An aluminum bracket needs anodizing or alodine, possibly painting, and ongoing corrosion inspection. The plastic part skips multiple process steps.
Where the plastics actually go
Cabin interiors — PEI (Ultem) dominates. Ducting, overhead bin components, seat frames, sidewall panels, window reveals, galley parts. PEI's natural V-0 flame rating at 0.25mm thickness, combined with very low smoke and toxicity, makes it the default choice for anything inside the pressure vessel. FAR 25.853 is the regulation that matters here — PEI passes it without halogenated flame retardants, which is a big deal because those additives make smoke more toxic.
Engine periphery — PEEK and polyimide. Not hot-section parts (those are superalloys), but everything around the engine: wire harnesses, connector bodies, sensor housings, bleed air ducting, bracket systems. These see 150-250°C continuous, vibration, and exposure to hydraulic fluid and jet fuel. PEEK handles all of that comfortably. For the really hot stuff (250°C+), polyimide takes over.
Structural brackets and fasteners — PEEK. When Boeing and Airbus started using more CFRP, they discovered that traditional aluminum fasteners were corroding at the CFRP-aluminum interface. PEEK fasteners and brackets eliminate the problem entirely. A PEEK bracket weighs about 65% less than the aluminum equivalent and doesn't corrode. The trade-off is lower absolute strength — you can't replace every aluminum bracket with PEEK, but for secondary structure and non-critical attachments, the weight savings are compelling.
Fuel system components — PEEK and PPS. Pumps, valves, seals, and housings exposed to jet fuel. PEEK's fuel resistance is excellent — it doesn't swell, doesn't degrade, and maintains mechanical properties. PPS is sometimes used as a lower-cost alternative in fuel system applications below 200°C.
Exterior and systems — various. Pitot tube housings (PEEK), antenna covers (PEI or PPS), hydraulic system seals (PEEK, PTFE), landing gear bushings (PEEK with bearing fillers). These are relatively small parts, but they add up to hundreds of kilos across the airframe.
What matters when you're the one speccing it
Aerospace qualification is slow. A new material might perform great in the lab but still take 2-3 years to get onto an aircraft. The testing burden is heavy: flammability (FAR 25.853), smoke density, toxicity, heat release rate (OSU 65/65), and often proprietary OEM specs layered on top.
If you're designing a part that might go on an aircraft, start the materials conversation early. Pick materials that already have aerospace qualification data — PEEK, PEI, and polyimide have most of the common specs covered. Custom formulations or less common polymers will add months to your qualification timeline.
We've supplied machined PEEK and PEI parts for aerospace applications ranging from cabin interior brackets to engine sensor housings. The surface finish and dimensional inspection requirements are typically tighter than industrial work — Class A surface on visible parts, 100% dimensional inspection on critical features. If you're working on an aerospace application and need a shop that understands the documentation and quality requirements, reach out.