Approximately 5 minutes into Avengers: Endgame we see Tony stranded in space recording a message for Pepper. In that message, he says that it’s been 21 days in space, the food ran out two days ago and the oxygen is going to run out tomorrow i.e. on the 22nd day resulting in his untimely death.
Here’s where it gets interesting; up until Endgame, Marvel Studios has made a total of 21 movies following the Infinity Saga storyline. Endgame is the 22nd movie and the last of the franchise. In the movie, Tony was going to die on his 22nd day in space, in reality, he dies in the 22nd movie! See the connection?
Coincidence? I think not! Well played Russo brothers, well played.