You can exit IPTraf-ng with the Exit command in the main menu.
When started with one of the command-line options to directly start a statistical facility, pressing X or Q will exit the facility directly, without any confirmation. The -t command-line parameter will automatically exit the facility after the specified length of time without any confirmation as well. Daemon facilities started with the -B parameter will immediately terminate after being sent a USR2 signal. See background operation in chapter 9 for more information.