How to answer this interview question??
I would go with "I applied for a couple of roles at the same time as applying for this, 1/2 of which have asked me to come for interview, although I feel that this role offers me X that makes it particularly of interest"
X could be company culture/roster schedule/bases/time to command etc which is relevant to that job.
If you are a first jobber then I can't think the airline would believe you if you said you weren't looking for any other roles. If you are already experienced then just consider how it looks if you are applying left right and centre. I think in that case you'd need to be able to give a good reason for multiple applications, like relocation to a specific place etc.
Best of luck