Hypersmurf
Moderatarrrrh...
How's that?
Well, it's not official. It's the opinion of a Savage Species author, and it makes sense, which lends it a lot of weight...
... but the official LA is +4, with or without wings.
Choosing to play a wingless Half-Celestial could be considered a little like choosing to play a Troll sorcerer - the ECL doesn't really reflect your power appropriately, like a Troll barbarian, for instance.
But you could petition your DM, and say "Look, I like this concept, but I know it's going to be underpowered... could we call it a +4 LA instead of a +5?"
Asking the DM to drop a wingless Celestial to +3 LA is perfectly reasonable.. but it's not official.
-Hyp.