 There are ARINC standards for ACARS on VHF and other data links installed on approximately 14,000 aircraft and a range of ICAO standards defined by the Aeronautical Mobile Communications Panel (AMCP) in the 1990s.Mode 2 is the only VDL mode being implemented operationally to support Controller Pilot Data Link Communications (CPDLC).The ICAO AMCP defined this Mode for validation purposes.