Spoilers for "Captain America: Civil War" and "Spider-Man: Homecoming".
In the first part of "Captain America: Civil War", Tony Stark tells Steve Rogers that
Pepper Potts left him (I assumed that the real reason was that Gwyneth Paltrow was sick of the MCU).
Later in the film, he meets
Peter Parker's Aunt May and starts openly flirting with her.
In the beginning of "Spider-Man: Homecoming", he constantly comments to Peter about how attractive he finds Aunt May, and I got the impression that they were planning on going somewhere with the May/Tony story, especially since he explicitly said that he saw himself as a father figure to Peter.
Then the May/Tony thread is dropped, and in the final scene of the movie
Pepper Potts suddenly pops out of nowhere, and Tony indirectly proposes to her by asking Happy to give her the ring he has been carrying since 2008.
Did I miss something?
Some of the commenters pointed out that Tony flirting with May is just Tony being Tony. Taken on its own, maybe, but there's also the fact that:
Tony mentions during one of the phone calls that he is trying to be a good father figure to Peter. Something along the line of "I'm trying to give you positive feedback, my father never gave me any..." or something similar (I can't find the exact quote)