The standard is five jets flying over as a sign of respect...and then one breaks off and four keep flying - as a sign of mourning.
Moments after the siren sounded, four jet fighters flew over my hours. One in the front, two slightly behind, and then the fourth on the left side, slightly behind...missing was his counterpart, the fifth plane that should fly on the right. It is a sign that someone is missing, that we go on, without the one.
I'm sure as the siren sounded in Mt Herzl - the national military ceremony (similar to Arlington for those in the States), these jets flew over, and the fifth broke away.
It must be a powerful thing to watch...a sad thing...something that brings home the lose of the one so powerfully. I watched the planes fly south over my house touched by the sight of them flying...and saddened for the ones who have been lost to us.