What appears to be a big emergency at the Des Moines airport Saturday night will be just a readiness drill.

Roy Kriss, a spokesman for the airport, says it’s a routine rehearsal, required by federal law. The Federal Aviation Authority requires every commercial airport to do a disaster-drill training every three years to give local emergency agencies a chance to rehearse their communications and the steps they’d take if that kind of event actually happened.

He says civilians will help make the drill more realistic. A group of volunteers will play the role of “victims.” Criss says it’s important to have people in the places and positions just like it would happen, should something like this actually occur. In addition to the first responders who might be called, Criss says there are dozens of airport workers who’ll benefit from having rehearsal of emergency rules and practices. They’re not all in the aviation department, but between people who work in operations, field maintenance, the 132nd Airborne, the airlines and rental-car companies, he says there are several hundred people who work on airport property.

The drill will take hours and reporters have been invited to observe some of the action for a time on Saturday evening. Scheduled flights will come and go as usual, so he says if you’re traveling and you arrive to board a flight or come in from a trip, it should be business as usual.