Unfortunately aviation has turned into a highly regulatory and litigation liable industry. If a pilot at an airline was ever unfortunately involved in an accident involving death of passengers the representative attorneys of the remaining families and their estates will use anything no matter how small in that pilots flying history to literally, and with no end in sight sue the daylights out of the airline. Every airline knows this extreme liability. Now there are over ten databases and counting that the airlines can track the pilots with. They are programmed to find even "investigation history" which by the way never expires in "outside databases". If a pilot in the future happens to trigger one of these database inquiries (that runs every 90 days) at the majors, then he is tagged for the rest of his career. So even if he thinks he's smart and doesn't select any of the "Death" boxes on the online airline applications it doesn't matter, because they will have him tagged on their "Questionable History" databases. "Conviction" or "no conviction" makes no deference to airline liability. Don't let the anyone tell you this goes away. An investigation may only be traceable for a year or so through government record request, that's why the outside databases for the airlines pull every 90 days. This way airlines can make it a permanent record for their hiring liability assessments. In the old days before computers were so powerful, you could dodge a few miss hit bullets from investigations but bottom line, those days are over, it is best that pilots keep a completely spotless record throughout their career. At the majors there are literally 80 pilots completing for each seat, being tagged by one of these databases makes it an easy "culling of the herd" process. Do your best to keep your record clean if you can.