The fact that Poland has been one of the United States' closest friends has been a source of tension between them and Russia. So the Russians are doing their best to show that they were not complicit in the plane crash that killed Poland's president and other top government officials. All indications are that fog and the pilot not wanting to disrupt the schedule of his country's most important dignitaries were the causes of the accident.
Still, God is in control and could have prevented this accident so He must have allowed it to happen for a reason. We will probably not know the full scope of that reason while we're in our mortal bodies but it appears to me at least part of the reason is that this reinforces our suspicions we are in the season when God is increasingly removing His restraint on evil in this world. Jesus said in Matthew 24:6-8 that the incidence of tragedies common to this fallen world would increase in frequency and intensity like birth pangs as His return gets closer.
The Apostle Paul reinforced this when he explained to the Thessalonians that God is keeping the government of the Antichrist from rising up through the ministry of the Holy Spirit who restrains evil... "For the mystery of lawlessness is already at work; only He who now restrains will do so until He is taken out of the way" (2 Thessalonians 2:7, NKJ).
The tragedy of losing a country's top government officials could have happened to any country. The fact that it happened to a close ally of the United States is just more evidence that God is allowing the influence of the United States to be diminished in the world. This is necessary to have a more level playing field between the nations of the world to make way for a worldwide government to emerge.
Even though God is removing His restraint on evil in the world, it doesn't mean evil has to affect us personally. Spiritual warfare is not new to followers of Christ; Ephesians 6:10-18 explains the resources God has given us "to stand against the wiles of the devil." We are entering a time when superficial faith will not be suffice... "Watch therefore, and pray always that you may be counted worthy to escape all these things that will come to pass, and to stand before the Son of Man" (Luke 21:36).