There is no way to mistake a Ukranian cargo plane for a jet liner at that altitude ? So whoever fired the missile knew what they were hitting ? Or as you state, it was a dumb mistake.
Whoever Shot Down the Malaysian Airlines Plane Probably Didn't Know What They Were Aiming At - The Buk is a Soviet-era air defense system used by both Ukrainian and Russian defense forces. “When you’re sitting behind a radar screen of one of these things, there’s no way to tell what it is. With the Buk, there’s no way to distinguish between friendly and foe. You’re just going to take a shot at it,” says Raymond Finch, a Eurasian military analyst at the Foreign Military Studies Office. “If [the separatists] had reports that the Ukrainians were flying over their airspace, they would shoot. It begs the question of who is sitting behind the trigger. Are they highly trained? My guess is no they are not.”If a Buk system was in fact used to shoot down the MH17, it must have lacked an automatic disengagement system that equips more sophisticated air defense missiles, designed to prevent deployment against civilian aircrafts. “A lot of these earlier systems don’t have that,” says Finch. “But they’re still highly efficient, especially against a civilian airliner.”