How beneficial is feeding past 1 year in terms of antibodies and immunity?

Hi everyone. My baby is 16 months old and I am still feeding a couple of times during the day. He would get like 6 - 7 ounces a day. Is it still protective of his health through the antibodies. The reason I am asking it, I will have to go on an international flight of 11 hours to Turkey. And unfortunately I do not have the peace of mind because of this swine flu threat. Would you suggest I increase the milk supply through pumping to give him better protection against virus or bacteria? Thanks for your answers...