Is there anyway to expand my MacBook Air's hard disk? I have a 2011 MacBook Air(11-inch), I am using OS X 10.9, but I only have 64GB Flash Storage, and I  want to expand the storage of MacBook Air's hard disk. I asked geniuses at Apple and they told me the answer is no. So, is this possible?
It is possible, although not from Apple themselves.

A company called OWC seem to specialise in SSD upgrades for macbook's and have upgrades for your model available here

These particular upgrades offer greater speed and capacity to some of the stock apple SSD's from 2011.