PRIMECAP Management Reports 10.02% Stake in Southwest Airlines (LUV)

Executive Summary

On October 5, 2026, PRIMECAP Management Co/CA/ filed Amendment No. 21 to its Schedule 13G with the SEC, disclosing a beneficial ownership position of 49,003,285 shares of Southwest Airlines Co (NYSE: LUV) common stock as of September 30, 2026. This represents 10.02% of the company's outstanding common stock.

Key Position Metrics

• Reporting Entity: PRIMECAP Management Co/CA/ (Registered Investment Adviser)
• Security: Common Stock (CUSIP: 844741108)
• Aggregate Beneficial Ownership: 49,003,285 shares
• Percent of Class: 10.02%
• Voting Power:
  • Sole Voting Power: 48,841,406 shares
  • Shared Voting Power: 0 shares
• Dispositive Power:
  • Sole Dispositive Power: 49,003,285 shares
  • Shared Dispositive Power: 0 shares
• Additional Interests: Vanguard PRIMECAP Fund holds an interest exceeding 5% of the outstanding common stock within the reported position.

Filing Context & Market Impact

1. Passive Nature: The filing was executed pursuant to Rule 13d-1(b), verifying that the shares are held in the ordinary course of business and not acquired for the purpose of changing or influencing control of the issuer.
2. Long-Term Holder: Being Amendment No. 21, this filing reflects ongoing portfolio management activities by a long-term institutional shareholder rather than a sudden activist campaign or new strategic position.
3. Trading Significance: Rated Low. Routine institutional amendments under Schedule 13G generally reflect periodic portfolio adjustments or index/fund rebalancing rather than corporate governance catalysts.