Iranian officials maintain it's 'scientifically impossible' for the Ukraine International Airlines flight to have been shot down by a missile

Justin Bronk, a research fellow at the British defense think tank Royal United Services Institute, tweeted Thursday that if the allegations are true, it shows "staggering incompetence and carelessness" to mistakenly fire at a commercial jet. "There is no excuse. Doesn't matter [if] it was during a US-provoked standoff," he said.