Re: assassinating important politicians?
the secret service do not protect senators or congress reps unless a special request is made... and there has to be a good reason ie - they're running for president. they do protect anyone who is an immediate family member of the sitting president (or past, if requested). senator hillary clinton got this protection for this reason.
when senator mccain was running for president he did NOT request secret service protection btw.
to make your story work, your senator should be in one of those 2 categories: related to the president or running for president.
in an airport they have separate terminals for private aircraft. many senators use private jets. some rich senators have their own but most often it's borrowed from a wealthy supporter or friend... or they can charter a private jet. strangely enough -- there is less not more security at these private terminals because the general public has no reason to go there. but don't tell anybody i said this.
hope this helps.