The average age of the U.S. military's F-16 fighter jets is 27 years. A recent study of 12 military aircraft by the U.S. Government Accountability Office found that as of 2016, "10 of 12 aircraft are experiencing sustainment challenges related to aging; all 12 are experiencing challenges related to maintenance; and all 12 are also experiencing challenges related to supply support." The study also found that between 2011 and 2016, the availability of these aircraft to conduct missions declined for 6 of the 12 aircraft.