Does my husband have a chance of winning an assault case in which he was the victim?

Sounds like you have an excellent chance of winning a civil case against the assailant, but what damages you will win, and if you will be able to collect, are undetermined.  You make no mention of monetary damages.  The airline or airport might be liable, if you can show some way in which one or both was negligent, and such negligence caused or contributed to the damages (for example, if their secutiry was insufficient and this led to the attack, or if the airline served alcohol to the assailant even after he was drunk, causing him to act irrationally, if they didn't get your husband medical attention quickly enough, etc.)  However, you should take a look at your ticket and any other paperwork to see if there is a limitation of liability provision.