Pushing back on a letter from three U.S. senators, Atlanta-based Delta Air Lines said Thursday that it is not, and has not, used or are testing an artificial intelligence system for ticket pricing.

Delta Air Lines has hit out at critics of its artificial intelligence ( AI) pricing tool after receiving backlash for using an alleged "individualized pricing" system. Last week, prominent US senators penned a letter criticizing the possible use of customers' personal data to set individual prices for fares.

The airline said it plans to deploy AI-based revenue management technology across 20 percent of its domestic network by the end of 2025 in partnership with Fetcherr, an AI pricing company. Delta Air Lines currently uses the platform for 3 percent of its domestic flights.