Titans revealed that Nightwing had a no-flying rule and it shows how Batman ultimately failed him. The former DC Universe series (now airing on HBO Max) established how angry and resentful Dick Grayson was at his mentor and father figure Bruce Wayne as early as season 1. They’ve on speaking terms as of Titans season 2, but Dick confirmed he doesn’t fly in season 3 and it paints a larger picture with regards to his relationship with Batman and how he grew up.
In Titans season 3’s third episode, called “Blackfire,” Dawn leaves Gotham City for Paris following Hank’s death, which was all a set-up by Jason Todd (now Red Hood). When Dawn tells Dick he could always come with her, he says that he hates flying. This makes a lot of sense in retrospect, especially considering how often Nightwing is shown driving from one location to another every season. However, the dialogue in season 3 speaks to something even deeper. Dick was taken in by Bruce after his parents died during their circus act. They were notably called the “Flying Graysons,” performing aerial stunts for a captivated audience every night.
The manner of their deaths left Nightwing with a lot of trauma and the fact that he still doesn’t board planes and doesn’t want anything to do with flying suggests he has yet to move on from what happened. Crucially, it highlights the fact that Batman, instead of helping his surrogate son move on from the pain and trauma of his past, weaponized it instead. Bruce channeled his own trauma into creating Batman and taking down Gotham’s criminals; he did the same thing with Dick, training him to become Robin, fueling his anger and hurt into fighting lessons and taking down bad guys. He never taught Dick how to get past that in a healthy way because he never did and it showcases the ways in which Batman didn’t do right by Nightwing at all.
In many ways, Nightwing is still dealing with the effect of his parents’ death and his refusal to fly as an adult — even though it’s completely safe to do so — means he has yet to overcome that lingering fear. What’s more, Dick has been trying not to be Batman for so long because he’s seen first-hand how not getting past one’s pain can be detrimental. The Dark Knight hasn’t exactly been constructive when it comes to helping the people he loves most and that’s effectively done more harm than good for Dick (and, by extension, Jason).
Dick’s hatred of flying is an extension of his childhood trauma and it’s possible that if Batman had aided Nightwing early on, he would have been able to recover from this particular fear and avoidance. Unfortunately, Batman was more concerned with funneling that trauma into unhealthy coping mechanisms. Dick sees this now in the way Bruce handled training Jason, but it was already too late for the second Robin, as evidenced in Titans season 3. To be sure, Batman could have done a lot better in handling Dick’s trauma, but if he couldn’t even get past his own, then it was always doubtful he would be able to properly help Nightwing overcome his.