The base has been the subject of security concerns in recent years amid rising global terrorism.
In 2016, a delivery driver was jailed for plotting to run down and then behead U.S. service personnel from the base in revenge for a friend who was killed in a drone attack in Syria. In 2015, July 4 celebrations for U.S. personnel at the base were canceled amid fears of an attack.
Alastair Jamieson reported from London. Hans Nichols reported from Washington, D.C.
Alastair Jamieson is a London-based reporter, editor and homepage producer for NBC News.