I wonder if those IL-76 Candids were delivering S-300 (S-400??) missiles and associated sensors etc., to the Syrian military? If so that will put a large very annoying burr under the Israeli (+ US & Coalition) seats. That most definitely would be one way for Putin to show his displeasure and there's nothing Israel, the US or anyone else can really do about it, except gnash their teeth, tear their hair and render their clothing. To attack the missiles would be an act of war, pure and simple and whilst casus belli could be reasoned (how would be interesting), it would be a very dangerous move. Such an attack could be deemed a war of aggression and it would give Syria
Jus ad bellum, a right to war, in this case self defence, giving Syria and it's allies the moral, political and diplomatic high ground. If these flights are indeed deliveries of S-300 missiles to the Syrian military, I do hope that cooler heads prevail in Israel and elsewhere.
We'll just have to wait and see what happens.