The Space Shuttle Carrier Aircraft, two modified Boeing 747s, were retired in 2012 with the end of the Space Shuttle program. They are now on display in museums. One is at the Joe Davies Heritage Airpark in Palmdale, California, and the other is at the Space Center Houston.
I have no idea how much it would cost to bring either of the two transport 747s back into service. I doubt it could be done for the amount mentioned in the bill.
Not to mention the support infrastructure that was installed at Edwards that would have to be created someplace in VA to mate the shuttle to the 747 and at same infrastructure would be needed in Texas. Both at airports that have runways to support the take off / landing of the 747 with the shuttle attached. Then you would need the ground transport to take Discovery from the museum where it is now... to the airport and from the airport in Texas to where ever they would put it on display.
Not to mention that while a piece of history, there is no plan at present to do something of a follow on to the STS that takes any of the lessons learned from the lives that were lost ( including my co-worker, Kalpana Chawla ) and make a new STS.
The entire idea is ridiculous.
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