Exhibit 99.1 ATN Reports Fourth Quarter and Full Year 2023 Results; Provides 2024 Outlook “First-to-Fiber” and “Glass & Steel” Strategies Drive Year-Over-Year Growth · Fourth-quarter revenues grew 4% to $199.0 million · Full-year revenues grew 5$762.2 million · Total high-speed broadband subscribers increased by 20% · Broadband homes passed by high-speed data services expanded by 33% · Capital expenditures for the full year were $163.3 million (net of$32.9 million reimbursements) Operating Income and ...