Southwest Airlines has said it could cancel 100 flights on Monday after small, subsurface cracks were found on three more jetliners, even as media reports said the airline has had maintenance issues.

The fuselage of a Southwest Airlines Boeing 737-300, which took off from Phoenix on Friday, ruptured minutes after takeoff, resulting in the loss of cabin pressure. The 5-foot-long crack on the upper part of the fuselage forced an emergency landing at the military base near Yuma. The Sacramento-bound aircraft was carrying 118 passengers. No one was seriously injured in the incident, which happened when the plane was 35,000 feet up in the air.

Southwest Airlines had canceled around 300 flights on Saturday and another 300 flights on Sunday as part of a hectic inspection regimen initiated in the wake of the Friday scare over Arizona.

Among the three planes with cracks on the fuselage are two Boeing 737-300s. According to a National Transportation Safety Board (NTSB) official, another plane too had a crack on the fuselage.

MAINTENANCE PROBLEMS

The Seattle Times said in a report on Monday that Southwest Airlines has a history of maintenance problems. The report said the Federal Aviation Administration (FAA) had proposed a $10.2 million penalty in 2008 for the airline's failure to conduct mandatory inspections for fuselage fatigue cracking on some of its Boeing 737s. Later the penalty was reduced to $7.5 million.

It also pointed out that, according to Federal Aviation Administration (FAA) records, the jetliner that involved in Friday's scare had fuselage cracks fixed in March last year. ..., the airline in March 2010 identified and fixed 21 cracks in the fuselage of the Boeing 737-300 involved in Friday's incident during a scheduled inspection that lasted more than a week, the report said.

It also said such fatigue cracks are not uncommon in older jets, citing experts.