Like text messaging for planes. Not 1090MHz and appears to be falling out of style... acarsdec Still parsing info from these, seem to be from mostly older planes which don't have adsb-out.
Mode : 2 Label : H1 Id : 5 Nak
Aircraft reg: N595UA Flight id: UA2795
No: F50A
#M2BREQPWI/TS040406,180418/WQ410.370.320:AEX.IAH.WEEED.WAILN.REDNK.RODIO.MARCS.BRAUN.TROOP.CRISS.JATAX.REUBE.HASDO.ALAMO.RW13R.EMBOW/DQ400C705
More modern ACARS replacment, can also carry ACARS messages. Seems to use IATA identifiers for flights instead of ICAO.
Very few messages actually have the 'depa' message:
{"timestamp":1546955433.4004121,"station_id":"piass","channel":3,"freq":136.975,"icao":10603978,"toaddr":1069434,"mode":"2","label":"QQ","block_id":"6","ack":"!","tail":"N215TM","flight":"XA0001","msgno":"M05A","text":"KHOUKLZU1350\r\n001FE08135016N2937.8W09517.30151850083","depa":"KHOU","dsta":"KLZU","wloff":"1350"}
{"timestamp":1547023078.402709,"station_id":"piass","channel":3,"freq":136.975,"icao":11362281,"toaddr":1063258,"mode":"2","label":"83","block_id":"2","ack":"!","tail":"N961AM","flight":"AM0008","msgno":"M17A","text":"EGLL,MMMX,090837, 29.44,- 95.52,34000,298,-151.3, 13100","depa":"EGLL","dsta":"MMMX"}
{"timestamp":1547036085.4382191,"station_id":"piass","channel":3,"freq":136.975,"icao":10674430,"toaddr":1053754,"mode":"2","label":"QQ","block_id":"0","ack":"!","tail":"N285EM","flight":"XA0001","msgno":"M05A","text":"KIAHKDAL1214\r\n001FE09121444N2957.9W09521.3---0180035","depa":"KIAH","dsta":"KDAL","wloff":"1214"}
{"timestamp":1547073568.572907,"station_id":"piass","channel":3,"freq":136.975,"icao":10638550,"toaddr":1070234,"mode":"2","label":"83","block_id":"8","ack":"!","tail":"N24972","flight":"UA0283","msgno":"M51A","text":"KSFO,KIAH,092239, 29.99,- 95.52, 2987,172, 82.5, 13100","depa":"KSFO","dsta":"KIAH"}