There have been a lot of rumors flying around about the Justice League runtime, with a whole lot of various placeholders being posted on theater websites.
Today the same source who correctly told me of the date that The Last Jedi tickets would go on sale informed me that theaters have been told that the Justice League runtime is 121minutes, or two hours and one minute. They are using this runtime to finalize showtimes, and tickets could go on sale as early as this weekend or on Monday. That’s earlier than the October 30th date that was previously reported.
The runtime could still be a placeholder and just something given to theaters for the purpose of programming tentative showtimes as some of the IMAX theaters show a three-hour gap between times. Also as the IMAX site is now listing showtimes, it’s very likely we will be able to buy tickets by Monday as that’s how it happened with The Last Jedi.