Joe and Anthony Russo, the directors of Avengers: Endgame, have confirmed the film is “at the three-hour mark,” though edits are still being made to the film.
In an interview with Collider, one of the directors said, “I think the studio is down with what the best story is. Right now, we think the movie is playing well and we’ve had great responses from our test audiences and we’re feeling very good about where it is. We’re still doing work to it. We’re not done with it.
“Again, this is a culmination film of 22 movies, it’s a lot of storytelling to work into it. Emotion is an intrinsic part of that to us. When you have to tell a really complicated story and you want strong emotional moments with the characters, it just requires a certain amount of real estate. This one, in particular, feels like three hours worth of real estate.”
Source: IGN.com Avengers: Endgame Could Be the Longest Marvel Movie Ever