Speaking as a
PR consultant I’d say clamming up helps no one.
A persistent journalist WILL keep calling around your company; it is after all their job. Eventually he or she will get a result, someone either foolish enough or vain enough to talk on a subject when they should not.
If you are called and are not authorised to comment be helpful, take a name, number and commit to calling back, ask for the journalist's deadline and try to find out who else has been spoken to. Then call your
PR contact (It's in the manual right?) and pass on the details, get them to call back or provide you with a set of agreed words or if the situation dictates a statement to read.
The key is to manage the process. Refusing to comment, ducking questions, guessing or worse lying are all at best unproductive at worse commercial / professional suicide. Providing timely accurate information will help squash scare mongering and reduce "an industry source" type speculation.
Any company involved in aviation would be well advised to build press relations into their crisis management plan. You should ideally practice implementing this - including involving local journalists - firstly this adds realism for your team, secondly its good training for the journalists (!), they will know where to come, who to expect to talk to etc and finally it's good to build the relationship.