Graybeard - Final Four Minutes of Reports
Active tracking Antenna's have been replaced by phase scanned microstrip patch arrays or similar for communication via the Inmarsat Satellite Network, and stub helical for LEO's such as Iridium and low speed Inmarsat.
So there is no need for any "tracking" or "pointing" of the antenna.
There are a multitude of data speeds offered, from 600bps up to 64kbps.
Air France may well have their own proprietary system for ACARS, but if using the Inmarsat System, then as you say, they will have been pretty much right below the AOR-E Satellite at 15 West (I believe the Aero service at this time is on the I-3 satellites not the newer I-4), so will have had a good "view" of the Satellite.
With the Satellite pretty much overhead, the signals would only be obscured if the antenna were to move out of its (pretty much) 150 degree (+/- 75) view of the sky. For those "Four Minutes" the aircraft (I'm presuming), could have been at any attitude just so long as the antenna's were within their field of view for the satellite.