The federal government operates Boeing 747-200s as Air Force One. The first one was delivered in 1990. The 747-200 itself (in military configuration, a VC-25) was first put into service in 1971.
Last year they entered into a contract with Boeing for two new custom 747-8s to become the new Air Force One.
Donald Trump, who may never get to fly in the new planes, criticized the deal this morning on Twitter.