Southwest Airlines grounded 79 airplanes on Saturday after a piece of the fuselage on one of its Boeing 737s ripped open during a flight the day before, leaving a hole in the cabin ceiling and rapidly depressurizing the aircraft.

“We’re taking them out of service to inspect them over the next few days,” Whitney Eichinger, a Southwest spokeswoman, said Saturday. She said they would be “looking for the same type of aircraft skin fatigue.”

In a news release, Southwest announced that it would cancel about 300 flights on Saturday because of inspections, and that customers should expect delays of up to two hours.

“The safety of our customers and employees is our primary concern,” Mike Van de Ven, Southwest’s chief operating officer, said in a statement. “We are working closely with Boeing to conduct these proactive inspections and support the investigation.”

The Southwest plane, a 15-year old Boeing 737-300, was cruising at 35,000 feet on its way to Sacramento from Phoenix on Friday afternoon when passengers heard an explosion. The Associated Press reported that one woman described it as “gunshotlike.”

The plane’s oxygen masks were released, and two people, a passenger and a flight attendant, passed out as the pilot descended to make an emergency landing at Yuma Marine Corps Air Station in Arizona.

Nobody was seriously injured, Ms. Eichinger said, and all 118 passengers chose to continue on to their destinations on Friday aboard a replacement jet.

Officials at the National Transportation Safety Board said the tear in the airplane’s skin was 5 feet long and 1 foot wide.

Officials from the Federal Aviation Administration and the N.T.S.B. were on the scene investigating, the F.A.A. said in a statement. Manuel Johnson, a special agent at the Federal Bureau of Investigation, said there was no reason to suspect terrorism.

Pictures of the airplane show that a flap of the aircraft’s skin near the overhead baggage compartments was peeled back.

“You can see completely outside,” one passenger, Brenda Reese, told The Associated Press. “When you look up through the panel, you can see the sky.”

Southwest Airlines’ fleet is made up entirely of Boeing 737s, and the 79 planes the company grounded were all 737-300s.

The emergency landing was not the only incident in the skies over the United States on Friday.

An American Airlines flight from Reagan National Airport in Washington to Chicago made an emergency landing in Dayton, Ohio, after two flight attendants told the captain they were feeling dizzy. Jim Faulkner, a spokesman for American Airlines, said they were investigating whether the plane had depressurized improperly. No other planes had been taken out of service.

And an Atlantic Southeast Airlines flight from Atlanta to Little Rock, Ark., made an emergency landing after hitting a flock of birds. None of the 48 passengers or three crew members on the regional jet were injured, and the plane was operating normally when it landed in Little Rock, said Kate Modolo, an airline spokeswoman.

CNN reported that the aircraft sustained substantial visible damage to its nose and that at least one dead crane was stuck to the front when it landed.

Regarding the Southwest incident, James E. Hall, a former chairman of the National Transportation Safety Board, said that the airline had “a good safety program,” but that the company worked its airplanes hard, scheduling flights with very quick turnarounds. “They pound their airplanes daily,” Mr. Hall said.

“The skin of the aircraft is like human skin,” he said. “Any type of puncture is serious.”

Two years ago, Southwest faced a similar episode when a hole ripped open in a plane’s fuselage and forced an emergency landing on a flight bound from Nashville to Baltimore. Earlier that year, Southwest was fined $7.5 million for safety violations by the Federal Aviation Administration.

In 1988, a flight attendant was killed and scores of passengers were injured when an Aloha Airlines Boeing 737 suffered a 20-foot rupture in its fuselage during a flight in Hawaii. The flight, carrying 89 passengers and a crew of five from Hilo, Hawaii, to Honolulu, was at traveling at 24,000 feet when the tear occurred.

The pilots sent an emergency message to air traffic controllers and then guided the aircraft to a safe landing at the Kahului airport on the island of Maui. The right engine had been knocked out of commission by debris from the fuselage section that had been ripped away.

One flight attendant was swept from the plane, but passengers grabbed second flight attendant to keep her from being pulled out too. Sixty passengers were hurt.

Jad Mouawad contributed reporting.