Travelers going through Baltimore-Washington International Thurgood Marshall Airport Saturday may see a lot more emergency vehicles and people in uniform than they're used to, But don't worry: It's a drill.

Emergency personnel and airport officials will be conducting an exercise simulating the response to an event such as an air crash between about 9 a.m. and 1 p.m.

Jonathan Dean, a BWI spokesman, said such drills take place every three years under federal rules. He said the drill is not expected to delay flights or cause any other disruptions for travelers.

The exercise will involve state, local and federal agencies, including the Maryland Transportation Authority Police and local fire departments, Dean said.