AMC is developing a standalone special set in the shared world of Fear The Walking Dead and The Walking Dead. The half-hour special / prequel will follow "a group of passengers facing a walker attack on an airline while in flight. One character who survives that encounter will then join the cast of Fear the Walking Dead in season 2."
The special takes place about the same time as Season 1 of Fear and will premiere online. It will also be shown on TV in separate segments during the ad breaks of The Walking Dead Season 6.
Not many details yet on the future Fear character, when exactly the special will air, we do know that showrunner Dave Erickson and co-executive producer (and writer) David Weiner will be part of the producing team for the special.