The two 747 planes currently serving as Air Force One were delivered in 1990. They are 27 years old. As planes age, they become less cost-efficient to operate, and malfunctions become a bigger possibility. The planes will need to be replaced at some point, and relatively soon. Even if new planes were ordered today, the old ones would be about 30 years old (give or take a bit) by the time the new ones would be delivered.