TransDigm is an aerospace aftermarket monopoly disguised as an industrial conglomerate. With ~90% proprietary products and ~75% sole-source contracts across 300,000+ active PMAs, the company possesses a legal monopoly on replacement parts for nearly every aircraft in service. The business model — acquire niche aerospace component makers, implement rigorous cost controls, and leverage sole-source positions for pricing power — generates 47%+ GAAP operating margins and 50%+ EBITDA margins, among the highest in any industrial sector. The $3.2B acquisition spree (Stellant + JPE/VSA) in early 2026 extends the playbook into PMA aftermarket, neutralizing the only credible competitive threat while adding ~$280M incremental revenue at TransDigm-level margins.