The Kremlin tends to play down these attacks, and has a history of offering unconvincing explanations for massive explosions that sometimes result.

Azerbaijan Airlines Flight 8243 was scheduled to travel from Baku, the capital of Azerbaijan, to Grozny, a city in the Russian region of Chechnya, on Wednesday, but was diverted and ultimately crashed on the other side of the Caspian Sea, less than two miles from the airport in Aktau, Kazakhstan.