An Israeli does not have two days Shavuos, remember it is the chutznikim who have two days, there really is ONLY one day. So leaving Israel on Isru Chag is no problem at all. The problem only “appears” when the passneger arrives in chutz la’aretz and finds himself in a land where yomtov is in effect. There are varying opinions here and one should ask their rov what to do. Some stay put in the airport till nightfall. Some leave the airport but try to be as inconspicuous as possible when they arrive at their destination. Of course some don’t even fly , thereby avoiding the situation.
