Polish President and Army Chief of Staff dead

[Carsten Wiethoff]

Commercial planes land in fog and rain all the time! Did the airport have a radio beacon and did the plane have the equipment to to follow it? More to the point, did someone sabotage the plane...a very easy thing to do these days! And all too often used....the danger on flights IMO is greater from the intelligence goons than from real 'terrorists' intent on taking a plane down. The intelligence goons ARE the biggest and most organized terrorists, but I digress......

There is an NDB at the airport. The minimum visibility for an NDB approach at Smolensk is 1000m. An NDB approach in the conditions reported would be dangerous and illegal. There may be PAR (precision approach radar), but a PAR approach means that the incoming plane is assisted by the ATC who has the radar view and has to talk back its altitude to the controller. It is not clear that this was the procedure used, it seems that at some point in the approach the plane stopped communicating with ATC.
The plane was equipped with ILS, but there is not an ILS (which is what would be used at most civilian airports in these conditions) nor a VOR at the airport.
Reference : http://avherald.com/h?article=429ec5fa&opt=0

So technically the conditions for landing were marginal at best, more likely illegal. But this, of course, tells us not, if there was foul play.
I can see means and opportunity, given the plane was overhauled in Russia in December. I even can get an idea of a motive, reading Jan's posts. This gives us cause for suspicion, and maybe a suspect, but that is still far from proof of foul play.

Both alternatives are possible, and even when the final report will be issued (and I don't doubt it will claim pilot error) both alternatives remain possible, because reports can be manipulated.
In the end it will be a question of likelihood and which evidence can be trusted.