i'm kinda new at this. i only became an SWLer this past summer. i assume from your reply this stuff is rare?
Yes, but the "stuff" he is referring to is actually hearing an emergency taking place while you are listening.
if so i was extremely lucky to catch it on my RSP1a SDR and MLA-30 magnetic loop antenna up here in Seattle. i know propagation conditions aren't the best right now but when they are at their peak is this stuff more typical?
Well, being able to hear the conversation is important but I don't think that this is what Josh was referring to. (See above.)
You are listening to one of the many transoceanic HF communication frequencies set aside for commercial aircraft. Each flight path zone has several frequencies allocated to it. (You probably already figured that out though.)
https://wiki.radioreference.com/index.php/MWARAThey do this so that at least one frequency of the many they are allocated will likely work well enough between aircraft scattered about and the land stations. They spend enough money on equipment, antennas and propagation forecasting to be sure that they
can maintain contact. So it's not surprising that you can hear the conversations but it's much more unlikely that you hear an ongoing emergency in progress.
I hope that makes sense.