The emergency event CDC Planes Grounded prevents players from moving by flight actions, as well as the Airlift event. The rules denote some specific exceptions such as the Dispatcher's ability, but do not mention the First Responder or his ability to move out of turn after an Epidemic. Is that ability prevented by this emergency event?
CDC Planes grounded states
Players cannot move by direct, charter, or shuttle flight (or the event airlift).
The First Responders ability is
• As an action, you may move to any city with a research station.
• Immediately after an Epidemic, you may – out of turn – move to the epidemic city and Treat Disease there (before Infections).
Neither of these abilities are a direct, charter or shuttle flight, and so should not be affected by planes being grounded.
This thread on boardgamegeek comes to the same conclusion.