h3dxb
For the Satellite Telephone system and other high speed connections I well believe there is an aimed antenna. ACARS could be using something like, but more modern than, Inmarsat-C which had a low data rate, small messages, and an omnidirectional antenna. It "sort of" makes sense to send ACARS through such a connection. That is why I believed it when someone else mentioned that ACARS used an omnidirectional antenna. Telephones (and Internet) would need a high gain steered patch antenna to be effective. For ACARS that might not be an issue.