(Reuters) - The U.S. Federal Aviation Administration (FAA) said on Friday it has begun a probe following an in-flight incident involving an older 737 aircraft manufactured by Boeing Co <BA.N> and flown by Southwest Airlines <LUV.N>.

The FAA said the aircraft was en route to Boise, Idaho, from Las Vegas on Monday and experienced a gradual loss of cabin pressure at one point before reaching the destination without any injury to the passengers.

An initial inspection of the aircraft by the FAA revealed a 12-inch crack on the crown skin in an area that already requires inspections every 1,500 flight cycles.

The Wall Street Journal reported (https://on.wsj.com/2WbqxiI) the aviation safety regulator was investigating potential structural problems affecting hundreds of Boeing 737 jets.

"The aircraft was taken out of service and is currently in maintenance receiving repairs," Southwest said in a statement.

(Reporting by Praveen Paramasivam in Bengaluru; Editing by Krishna Chandra Eluri)