Defense News reports that "the US Air Force has grounded over half of its F-16D Fighting Falcons, the service’s Air Combat Command (ACC) announced Tuesday."
"The initial damage, described in a Pentagon release as 'canopy sill longeron cracks found between the front and rear pilot seats,' was discovered after a routine post-flight inspection on one of the jets. The discovery of cracks led to a fleet-wide inspection order."
"Of the 157 F-16Ds in the fleet, 82 were found to have cracks and have been ordered to stand down. The remaining 75 have been cleared to resume normal activities."