It's also not generally that easy. There's more than one system required to operate flights, usually more than 10. Some would be in BA data centers (UK), some in Amadeus/Altea data centers(DE), etc. Some applications are vendor provided, some in-house. So, you can have two of everything. But when you have something big, like a power outage, getting everything talking to the "surviving/dr" instances of all the different sytems isn't easy. And, the outage itself causes a huge spike in client driven transactions. Every passenger and employee is hitting whatever the equivalent of a reload button is.
The fix is more expensive than any major airline has been willing to spend thus far.
