This airline reservation UML sequence diagram shows the interactions among the customer, reservation system, airline system, and payment gateway. The process begins when a customer searches for flights. Upon selecting a flight, the system checks seat availability with the airline. If available, the customer pays. This interacts with a payment gateway to process the transaction. After confirming payment, the system will book the reservation and email the customer a confirmation. If payment fails, the system notifies the customer. This diagram highlights alternative and failure paths for a smooth customer experience.