Baltimore air traffic control tower struck by lightning

Subsequent tweets attributed the closure to an "Air Traffic Control equipment outage." 

"As of now we have no opening time.. Will advise.." the airport tweeted at about 4 p.m. on Thursday.

The airport provided another update at about 5 p.m. stating that the air traffic control tower had been repaired.

"BWI Marshall Airport is Open," the airport tweeted. "Two Runways remain closed but air traffic is moving."

"Airline flight operations are expected to resume shortly here @BWI_Airport," the airport followed up in a separate tweet.