Exhibit 99.1 ATN Reports First Quarter 2024 Results; Revises Full Year 2024 Outlook “First-to-Fiber” and “Glass & Steel” Strategies Drive Continued Year-Over-Year Growth in High-Speed Data Subscribers and Network Reach · First quarter revenues increased 1% to $186.8 million · Total high-speed broadband subscribers increased by 12$36.0 million (net of $13.5 million reimbursements) First Quarter Results Impacted ...