Its specially modified specifically to carry that. Plus the shuttle generates lift of its own with its wings I think so its less weight than it really is. Not sure 100% though. But yeah extra baggage is BS they can handle way more than what they put in them
I know it's dead but I have to clarify this.
Airlines aren't charging for oversize luggage because the planes can't carry them, if weight was that tight the plane wouldn't be allowed off the ground. The baggage allowances are for balance, there is an allowed weight for planes after they're fueled and prepped, that is then split into the average passengers weight so that the plane isn't unbalanced, then there's the same with the baggage, all bags are weighed and put onto the belt so that the plane's weight distribution is correct to save as much fuel and money as possible, it also makes the aircraft easier to fly.
Airlines aren't charging for oversize luggage because the planes can't carry them, if weight was that tight the plane wouldn't be allowed off the ground. The baggage allowances are for balance, there is an allowed weight for planes after they're fueled and prepped, that is then split into the average passengers weight so that the plane isn't unbalanced, then there's the same with the baggage, all bags are weighed and put onto the belt so that the plane's weight distribution is correct to save as much fuel and money as possible, it also makes the aircraft easier to fly.