Horizon: Flight operations get a makeover
Horizon, the airline's name for its revamped FOS, is, if possible, even more complex than the PSS, says Tracy Hassell, managing director for the Horizon program and another direct report to Leibman. "The FOS let us run the airline, but every time we wanted new functionality it would take several months and a lot of money to go do it. We needed to do something differently and mitigate that," she says.
The FOS covers four broad functional areas: flights, crew management, cargo and maintenance, and engineering. The current mainframe runs an older version of IBM's Transaction Processing Facility software. "It is all one big database and it's not relational. That created constraints for us," she says.
The flat-file database makes tight integration between applications and the file system challenging, because there's no SQL interface to abstract the application layer from the database layer, as SQL-compliant databases do, she says. So rather than being able to define new SQL interfaces to the database, American has always had to create a custom application layer. "This has made the integration of new applications with the legacy FOS very complex and expensive," she says.
American began the initiative in 2007 with the development of an enterprise service bus (ESB) it dubbed Flight Hub. The ESB uses IBM products -- including WebSphere, Message Broker, MQSeries messaging and Application Server -- as its core components. It also uses IBM's Data Power for service management.
American built the system on instances of Red Hat Linux Enterprise running within VMware virtual machines hosted on x86-based blade servers, and has a few machines running Windows Server for off-the-shelf applications that require it.
At some point, Jetstream too will have its own ESB, Customer Hub, a new cargo system will have Cargo Hub, and so on. These ESBs serve as transport mechanisms that connect to all related applications and enable real-time data sharing between applications as well with other ESBs and with the mainframe.
Flight Hub is highly available, highly recoverable and runs simultaneously in more than one place -- unlike the mainframe, which offered redundancy within a single data center but had no backup site. "The program objective was to enable true disaster recovery," Hassell says.
The Flight Hub ESB consists of three main components. Applications can access data on demand, receive information on a regular schedule and send and receive data through topic-based publish/subscribe messaging. In the latter case, applications can subscribe to or publish information to update current flight times or let staff know when a crew can no longer legally continue to fly because they must rest, for instance. "The Horizon architecture uses standard distributed [computing] patterns using message queues and service calls between components," Hassell says.
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