It may be some T-38’s on a training mission for NASA and the FAA.
Via NBC Washington:
Expect to hear a couple of T-38 jets flying above you Thursday morning.
NASA and the Federal Aviation Administration will conduct flights on Thursday over the D.C. metro area. The flights are for training and photography, and will fly approximately 1,500 feet above us.
You can expect to hear the jets between 9:30 and 11 a.m.
“These flights are being flown in preparation for the arrival of space shuttle Discovery atop its 747 Shuttle Carrier Aircraft on April 17,” said a NASA spokesperson. “The T-38s will help determine the viability of possibly flying Discovery around the Washington metro area before landing at Dulles International Airport.”
Should the flights be canceled for any reason, they’ll be rescheduled and another notice will be released.