Interesting to note: At this point we are asking who staged the wreckage whereas before, at least myself, I was wondering how can both the wreckage and the survivors exist. I think you need to also consider the possibility that Widmore has staged the wreckage.
Also remember the message: Don't trust the captain.
Why would Widmore stage it? It seems Ben has motive enough, and possibly capability of pulling it off, but Widmore may have reason as well for covering up the crash of 815. Perhaps he learns of the crash, or even plans it, and immediatley begins covering it up by planting a fake plane, etc. This would keep the island off of the maps so he could learn how to exploit it unhindered by media and whatnot, and free to wage war on Ben and the others.
It is quite possible that Widmore is one of the original founders and investors of the island, and is trying to regain control after Ben's "revolution". Dropping a Boeing into this mess is a sure way to pick apart its inhabitants, especially if you hand-pick the passengers.