Zunum Aero v. Boeing — Ninth Circuit denies rehearing and confirms its jurisdiction

Case
Zunum Aero, Inc. v. The Boeing Company; Boeing HorizonX Ventures, LLC
Court
U.S. Court of Appeals for the Ninth Circuit
Judge
Johnnie B. Rawlinson (Bill Clinton, 2000); Bridget S. Bade (Donald Trump, 2019); Lucy H. Koh (Joseph R. Biden, 2021)
Date Decided
August 26, 2026
Docket No.
24-5212; 24-5751
Topics
Appellate Jurisdiction; Patent Inventorship; Trade Secrets; Supplemental Jurisdiction
Source
Read the full opinion

Background

Zunum Aero sued Boeing in Washington state court, alleging that Boeing misused confidential information concerning Zunum’s hybrid-electric aircraft technology. Zunum asserted Washington-law claims including trade-secret misappropriation, breach of contract, and tortious interference. Its allegations included—but were not limited to—a theory that two Boeing patents contained information taken from Zunum.

Boeing counterclaimed for declarations that its personnel were the sole inventors of the patents and removed the case to federal court. The district court granted Boeing summary judgment on those counterclaims, but a jury later found for Zunum on several state-law claims and awarded more than $92 million. After the district court set aside the verdict through judgment as a matter of law and conditionally granted a new trial, the Ninth Circuit reversed. Boeing then argued for the first time in its rehearing petition that exclusive appellate jurisdiction belonged to the Federal Circuit.

The Court’s Holding

The Ninth Circuit denied panel rehearing. It held that Boeing’s inventorship counterclaims arose under federal patent law but were permissive, not compulsory, because they did not arise from the same transaction or occurrence as Zunum’s claims. Zunum could—and did—prevail on trade-secret theories without disproving Boeing’s patent inventorship, so the claims lacked the substantial factual overlap required for compulsory counterclaims. The panel concluded that the same result followed under both Ninth Circuit and Federal Circuit precedent.

Because the patent counterclaims were not compulsory, they did not place the appeal within the Federal Circuit’s exclusive jurisdiction under 28 U.S.C. § 1295(a)(1). The panel also held that permissive counterclaims can support supplemental jurisdiction when the state and federal claims share a common nucleus of operative fact. That requirement was met because all the claims concerned Boeing’s access to and alleged misuse of Zunum’s confidential aircraft-technology information. Judge Bade agreed with the jurisdictional result and denial of rehearing but wrote separately to disagree with the majority’s compulsory-counterclaim analysis.

Key Takeaways

  • A patent-law counterclaim gives the Federal Circuit exclusive appellate jurisdiction under § 1295(a)(1) only if the counterclaim is compulsory.
  • Boeing’s inventorship counterclaims were permissive because Zunum’s broader trade-secret claim did not depend on defeating Boeing’s claims of sole inventorship.
  • A district court may exercise supplemental jurisdiction based on a permissive counterclaim when the federal and state claims share a common nucleus of operative fact.

Why It Matters

The published order preserves the Ninth Circuit’s earlier reversal of the post-trial rulings that had vacated Zunum’s jury verdict. More broadly, it clarifies that the compulsory-counterclaim test governing Federal Circuit appellate jurisdiction demands more factual overlap than the constitutional test for supplemental jurisdiction.

The decision also aligns the Ninth Circuit with the First, Second, and Seventh Circuits in holding that a permissive federal counterclaim may support supplemental jurisdiction over related state-law claims.

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