We temporarily removed the Aerwhale mob and spawn egg from the game in one of the 1.7.10 updates as they were causing major lag issues. The entities would get lost in chunked and pile up. When those chunks were loading, you'd see hundreds of them causing client & server lag. We'll add them back whenever we can design them better.

Thank you so much for the info!

Anytime! I recommend you visit our official website if you ever have questions. You'll get better support there!

http://www.AetherII.com

wait so i can do a command similar to /summon Aerwhale to spawn one?

You could if they were actually in the mod, but they were literally removed completely.