Lightning struck Baltimore-Washington International Thurgood Marshall Airport's air traffic control tower, injuring one person and shutting down the airport for nearly three hours Thursday afternoon, delaying or stranding thousands of travelers.

A bolt struck the tower about 2:30 p.m., shocking a controller as he was flipping a switch to turn on a generator that powers backup runway lights, said John Dunkerly, president of BWI's chapter of the National Air Traffic Controllers Association. The controller, whom he declined to identify, fell to his knees and experienced numbness in his left arm and leg, Dunkerly said. He since has recovered and was released from the hospital Thursday evening.

To avoid the risk of other injuries, the tower was shut down, prompting airport officials to ground all departures and divert all incoming flights.

Air traffic resumed about 5 p.m., though the control tower remained out of commission, according to the Federal Aviation Administration. The Potomac Terminal Radar Approach Control, which handles air traffic control in the air space around the Baltimore and Washington, D.C., region, assumed control of BWI air traffic, the FAA said.

On Friday morning, Jonathan Dean, a spokesman for BWI, said the airport's control tower was "fully staffed and operational" again, but he did not know exactly when operations were restored. The FAA did not immediately respond to a request for updates.

The lightning strike dumbfounded the controllers on duty Thursday, said Dunkerly, who added that he has never heard of such an incident in nearly 30 years in the industry. It also underscored concerns about safety in the 30-year-old tower, he said.

"We didn't have any idea why it happened," Dunkerly said. "Usually [the towers] are pretty safe during these storms."

Delta passenger Mark Levine, of Alexandria, Va., was on a plane readying to take off for Cincinnati when the pilot told passengers of the lightning strike, he said. The plane spent more than two hours on the runway without air conditioning before returning to a gate, Levine said.

Having missed a connection to Nashville, Tenn., Levine tried — unsuccessfully — to find another flight, then returned home to try again Friday.

"There's still thousands of people at BWI who are in line," Levine said Thursday evening.

Steve Sarkady of Atlanta had boarded a flight that was scheduled to take off at 12:50 p.m but was running late.

"We heard a couple loud booms around the airport," said Sarkady, who grew up in Rockville and was in the area on business. "It actually felt like it hit the plane."

The passengers were kept on the plane for more than an hour, and then the crew said they would take off. But they later told them the flight was canceled because of the lightning strike.

He planned to leave for Atlanta again Friday afternoon.

"I'll just roll the dice for tomorrow because today was just way too much," Sarkady said.

Shortly after flights resumed at the airport, travelers were scrambling to rearrange plans, making calls on cellphones and lining up at ticket counters. Dozens of flights were canceled, both arrivals and departures, with many others delayed by hours, according to flight tracking website FlightStats.com.

Lacey Shaver, 28, sat on the floor near the airport lost-and-found office, charging her phone. The Washington, D.C., resident was headed to Memphis, Tenn., for a high school reunion and a work conference on urban sustainability.

But she had a problem checking her luggage, and there was so much confusion during the outage that she wasn't even sure whether her flight had taken off.

"I have no idea if it's canceled," she said as she waited for ticketing lines to shorten so she could figure out her next steps. "In about 30 or 45 minutes, I couldn't find anyone to talk to."

St. Louis, Mo., resident Joe Blaes was planning to return home from a business trip when his 3:50 p.m. American Airlines flight to Dallas was first delayed and later canceled. Blaes, chief editor of Dental Economics magazine, said BWI officials handled the situation well and kept travelers informed. He is staying at a hotel Thursday night and intends to fly home Friday.