The company, Radixx, said it noticed “unusual activity” around its reservations program on Tuesday. It did not describe the malware or say how it got into the program.

A spokeswoman for Radixx’s parent, Southlake, Texas-based Sabre Corp., said Friday that the company was beginning to restore service to airline customers. Kristin Hays said the company reported the incident to the FBI.

Radixx said its system operates separately from those used by some larger airlines that are Sabre customers. Radixx said customer information wascustomer information not compromised.