Ukrainian hackers have hacked into the Russian database of the Sirena-Travel booking system, obtaining information on 664 million flights over the last 16 years. They also obtained the names, phone numbers and document numbers of the passengers.
News of this was posted on the Telegram channel of the hacker community KibOrg. An unknown group called Muppets, which is associated with KibOrg, is allegedly behind the hack.
Source: Yahoo News