I currently work as a crew controller, so I'm working with an active roster but not as a crew planner like the position you're applying for. However I hope you'll find these points useful.
1. Human skills. Crew planning/control is a HIGHLY unappreciated job, crewplanners/controllers are probably one of the most disliked people in the airline business by the crews and some will think you're on a personal crusade agains them
So good human skills are essential to keep a good relationship with the crews, you are indeed working in the same company, towards a common goal.
2. Creativity. Some schedules call for creative pairings. Pairings is what you would also call trips, and can be everything from one round-trip to many legs, starting and ending at the crewmembers' base. Your job would be to create (and assign) pairings that get the most flight hours out of each crewmember: Maximum duty periods, minimum rest (no wonder we're not popular
)Try to avoid alot of deadhead or excess hotel time, that costs money.
To know your limits in scheduling, you will be required to read and understand to fullest extent the pilots and f/a contracts regarding flight time limitations and crew-rests. If you have any experience in reading and interpreting law-texts, that would bevery useful
3. General aviation knowledge. Of course you'll learn more as you get on the job, but to be familiar with rules regarding pilots annual checks, typeratings and licenses, cabin crew training and recency, diffrence between aircraft types etc. will give you a definite edge.
4. Good computer skills. The computer programs used in crewplanning are not highly complex, but they are, lets say, different
If you learn to use the system properly and take full advantage of them, you'll make an excellent planner. So being able to quickly adapt to new computer programs is a plus.
5. Co-operation with other crewplanners. United has probably many planners, working on different bases and different crews (some will handle pilots, other cabin). As a crew planner, you have to be able to work closely together to keep the show on the road.
Good luck on you interview