Is my dog too big to bring in the cabin?

I’m planning on flying with my dog for the first time in a couple of months and I’m not sure if I will be turned away at the airport for him being too big for the carrier requirements. He’s a maltipoo and about 15 LB. I bought a dog carrier that is 18x11x11. He has room to lay down and can fully turn around with the top closed. He just can’t stand up and put his head up all the way.

If an airline employee can take a look at these pictures of him in the carrier and let me know if he will pass the inspection that would be very helpful.
dog photos