Israel has been studying satellite photographs of Iran for decades. When a new Iranian nuclear site appears, Israel’s first-class intelligence agencies can pick it out as quickly as an expert bird watcher can detect a new species of fowl in its area.
So, if a giant Malaysian aircraft with 239 passengers aboard has landed in Iran, the Israelis would know about it by now. But why should they share their knowledge with the world until they’ve checked the whole thing out for themselves? In the meantime, Israeli airline experts like the ones quoted in this article can deliver wonderful ads for the safety and superiority of El Al.
Most likely a number of countries know where the plane is. They can’t let on because to do so will expose their intelligence capabilities.