Having worked at SABRE its not as easy as you think, as there are a crapton of systems and people that depend on all that old stuff to keep running as it. SABRE

Having worked at SABRE its not as easy as you think, as there are a crapton of systems and people that depend on all that old stuff to keep running as it. SABRE has spent 30 years trying to modernize their mainframe based system piece by piece. But the core reservation system is actually highly available still, it's the modern bits that wind up less stable. The problem is that travel is a highly interconnected system of many different companies in which complexity is almost impossible to avoid. There are also many systems involved not visible to the public, such as weight balancing, crew scheduling, etc where even one of those failing and screw up airline travel worldwide. It's not always reservations or checkin that's broken, even something as simple as an airport system failing can have a domino affect all over the country.