WASHINGTON — A federal safety investigator says on-the-job naps should be considered as part of a plan to address fatigue by air traffic controllers, airline pilots and others who work overnight shifts.

National Transportation Safety Board member Mark Rosekind said there is a wealth of scientific studies that show short naps of between 20 and 30 minutes refresh workers suffering fatigue and help them remain alert when they return to their duties.

Rosekind is an internationally recognized fatigue expert who formerly worked for NASA and directed a sleep research center at Stanford University.

Since late March the Federal Aviation Administration has disclosed at least five cases of controllers falling asleep on the job. In two cases the controllers were fired.

FAA Administrator Randy Babbitt has said he won’t sanction on-the-job naps.