During the pilot, when the flight 828 landed, many children are seen in the field meaning that they were aboard. Here no child (or teen since 5 and a half years have passed) is seen on the flight. The youngest person aboard of the new 828 seems to be TJ that was already a universitary student during the time of the original flight.
After the plane lands T.J. sees a younger Olive and calls her by her name and she is excited that the remembered it. However she never told him her name so she would have thought it was weird that he knew it.