Until very recently, the searching has been done based upon information from the last radar pickup, and upon supposed wreckage sightings that have turned out to be false or fake. Obviously, that's different data than the actual last piece of information, which was an electronic ping. Approximately six hour difference between the last radar information and the last electronic ping.
The last electronic ping is what's most important, obviously, versus the last radar reading. The last radar reading is where the transponder was turned off, whereas the last electronic ping is, at the very least, more recent activity.
According to information from Reuters, the electronic ping would not indicate whether the plane was in the air or on the ground.
For an explanation as to why exact data wasn't recorded from that ping, according to information from Reuters, "...no data links were opened, the sources said, because the companies involved had not subscribed to that level of service from the satellite operator."