TransDigm Group (TDG) shares plummeted 5.71% in pre-market trading on Tuesday following the announcement of CEO Kevin Stein's retirement and the release of mixed second-quarter results for fiscal 2025. The aircraft parts maker's stock decline comes amid broader market concerns over potential pharma tariffs.

TransDigm reported second-quarter adjusted earnings per share of $9.11, beating analyst estimates of $8.95. However, the company's revenue of $2.15 billion fell short of the expected $2.17 billion. The 6.9% organic growth and reaffirmation of fiscal 2025 guidance were not enough to offset investor concerns.

The unexpected news of CEO Kevin Stein's retirement, effective September 30, added to the market's unease. Stein, who has been with the company for 10 years in senior leadership positions, will be succeeded by current co-Chief Operating Officer Mike Lisman. While Stein will remain on the board and serve as an advisor until March 2026, the leadership change appears to have rattled investors.

Despite TransDigm's statement that they "do not anticipate a material headwind from tariffs that we are unable to mitigate," the broader market concerns over potential pharma tariffs announced by President Trump may have contributed to the negative sentiment. As the company navigates these challenges, investors will be closely watching how the leadership transition and potential trade tensions might impact TransDigm's future performance.