Investment firm Calamos Advisors LLC increased its stake in Delta Air Lines by 12.2% during the second quarter, acquiring an additional 39,650 shares, according to a recent SEC filing. This purchase brought their total holdings to 365,245 shares, valued at approximately $17.96 million. Similarly, SBI Securities Co. Ltd. also boosted its position in Delta by 19.6% in the same quarter, adding 5,463 shares. These transactions are part of a broader trend of institutional investors modifying their holdings in the airline. No significant market reaction to these specific filings was noted in available reports.