DALLAS, Texas (CBSDFW.COM/AP) — Safety officials are investigating how a 12-inch crack appeared in the skin of a Boeing 737 jet operated by Southwest Airlines.

The plane gradually lost cabin pressure on the flight, but pilots flew down lower where the pressure was safe, and completed the flight from Las Vegas to Boise, Idaho.

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The oxygen masks never dropped down, and officials say no injuries were reported in the incident, which happened Monday.

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The Federal Aviation Administration says it’s looking into whether the area of the plane where the crack occurred should be inspected more often than once every 1,500 flights.

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