Hackers infiltrated the computer systems of travel reservations distributor Sabre and carrier American Airlines, but the companies have denied any sensitive information was taken.
The incident was consistent with incursions by China-based hackers that recently targeted insurer Anthem and the US government's personnel office, according to Bloomberg, which first reported the breach.
"We recently learned of a cyber security incident," Sabre said in a statement.
"At this time, we are not aware that this incident has compromised sensitive protected information, such as credit card data or personally identifiable information, but our investigation is ongoing."
Sabre, a former American Airlines subsidiary that was spun off in 2000, operates IP addresses still registered to American's name.
However, American Airlines spokesman Casey Norton said the carrier has found no evidence that its customer data might have been compromised.
"American has worked with outside cyber security experts who checked digital signatures, IP addresses and the style of attack, and there's no evidence to suggest a breach similar to that experienced by the US Office of Personnel Management," Norton said.
"Not in light of today, but because of prevalent attacks in the industry, we have redoubled our efforts and brought in more cyber security experts to investigate and defend our systems."
In June, US investigators said the attackers who allegedly stole sensitive data from the Office of Personnel Management used the same tool in the earlier data breach of US health insurer Anthem.
The Anthem attack was tied to a group that security researchers said is affiliated with China's Ministry of State Security, which is focused on government stability, counter-intelligence and dissidents.