"Many factors go into the decision to proactively cancel flights. At the time this decision was made, transit was down and school had been canceled" for city students, Southwest said in a statement.
"We wanted to ensure Employees and Customers had time to make arrangements and arrive safely," the airline said. "Our top priority is the safety of our Employees and Customers."
All of the flights were scheduled to depart the airport before 9 a.m. Tuesday, April 28. That day, Baltimore City Public Schools were closed, as were parts of the Maryland Transit Administration's Metro system.
Many airport employees live in the city and commute to the airport via public transportation.
Jonathan Dean, a BWI spokesman, said he was not aware of any other airlines canceling flights, and airport operations were not otherwise impacted by the unrest in the city. Southwest operates more than 70 percent of the flights into and out of BWI.
Southwest said it had encouraged fliers to check the status of their flights throughout the week, but not everyone got the message.
Michael Pachino, of Owings Mills, said he arrived at BWI on Tuesday morning for a 6:25 a.m. connection to Chicago, bound for business in Arizona.
When he saw the flight was canceled, it didn't make sense to him, and little information was forthcoming, he said.
"It was really strange, just the way they were not giving me a lot of information," the food manufacturer said. "The first person I spoke with said, 'It's because of the riots last night.' I thought that was really weird. That's a lot of money for the airline to lose."
A Southwest spokeswoman said the airline would not comment on the cost of the cancellations. Gov. Larry Hogan has estimated 200 businesses were damaged in the unrest, and economist Anirban Basu, CEO of the Sage Policy Group, has estimated businesses lost tens of millions of dollars because of a curfew established in the city for five nights.
Though BWI operations were not impacted, the Maryland Aviation Administration did send BWI fire and rescue department personnel and equipment to the city, and personnel at Martin State Airport worked overnight hours to fuel law enforcement helicopters, Dean said.
The MAA also supplied light towers during the demobilization of the National Guard, Dean said.
Pachino said he eventually got on an afternoon flight last Tuesday and made it to Arizona. When he wrote a follow-up email to Southwest to inquire about the cancellation, he was told it was for "operational safety," he said.
Pachino said he's not upset about the cancellation as much as he is with what's going on in Baltimore. "My inconvenience is minimal compared to what everybody else is experiencing, so it's not a big deal," he said.
In his ongoing travels for work, he's already noticed a change in how people respond when he tells them he is from the Baltimore area, he said.
He used to hear, "Oh, I love The Wire," or get questions about the Ravens and Orioles, he said. This week, he got what seemed like pity, he said.
"There was this changed reaction that I've never experienced, almost like, 'Oh, God, that's too bad,'" Pachino said. "And I'm like, 'That's horrible!'"