Skeleton??. Dont create it at all. Use rmic with an option for creating stubs only.
Record locking must be implemented using the methods public void lock(int) and public void unlock(int). These methods are required to allow concurrent use of the database when booking flights from multiple clients...
Normally in an MVC design, it is the model which models the data (and hence has all the accessor / modifier methods).
I noticed that you are using the 'this' reference to track ownership of the lock. This implies you have one instance of the Data class per connected client. If I am wrong then the remainder of these comments do not apply.