So he will be about 9 months old when you go? It's difficult. Three months is a long time for a hamster to live somewhere else - on the other hand he is young enough to adapt to the change of new environment and the change back to you afterwards. If he was older I thought he'd be better being rehomed rather than two changes. I just think it would be a bad experience for a hamster in the hold of a plane, and although you'd miss him, at least you'd know he was safe and there when you come back. You maybe need to try and find someone who already has a hamster so would be happy to hamster sit for 3 months and knows about hammies
In the hold he could also be in with cats, dogs and other animals - pretty scary.