I was originally responding to your comment that: 'The security agreements they signed are sufficient to guard national secrets.'

High ranking officers can just as much buy plane tickets as anyone else. Yes, including to countries that may not have entirely harmless intentions.

Signatures on a piece of paper are not the final arbiter of disputes between countries, as demonstrated by the previous administration. Even if they were, not everyone can be trusted 100% just because they made promises to that effect, actions speak louder than words after all.