Not necessarily. If it was military it could have been a small team on a small craft perhaps testing a new system and it went awry. Again, I have no idea. But it’s plausible.
I don’t think they test missile systems on active flight paths. I could be wrong about that.
In a conspiracy, it is necessary to have the fewest people involved as possible because someone always eventually talks.
A bomb is the most plausible conspiracy theory.
Thing is, it can only be a conspiracy of one ... anymore than that good luck keeping it secret no matter what. It will come out ...
PS - same thing happened to a B737 in Manila - tank blew up on the flight line ...
So if you're going to test a new missile system then you do it by shooting into the busiest air traffic corridor in North America? Good plan. </sarcasm>