The inspections of 79 planes followed an April 1 emergency landing in Arizona of a jet with a hole in its fuselage. Flight 812 was heading from Phoenix to Sacramento, California, when a 5-foot tear opened up 20 minutes after takeoff.

The discount airline canceled more than 650 flights in recent days as it checked the planes for fuselage cracks and fatigue.

"We're operating on a full schedule today," spokeswoman Whitney Eichinger said Tuesday.

The U.S. government will order emergency checks of some 737s for the kind of fatigue cracks that prompted the Southwest grounding. The Federal Aviation Administration directive on 737-300, 400 and 500 fuselage inspections, expected on Tuesday, will apply to the most frequently flown models.

It involves a time consuming and repetitive electromagnetic check not previously required for the area of the plane in question.

Southwest shares were off a penny at $12.45 in morning trading, and Boeing was off 18 cents, or 0.2 percent, at $73.77.