After a Southwest Airlines plane had to make an emergency landing in Arizona, inspectors found small subsurface cracks in three other Southwest Airlines planes on Sunday, the Star Tribune said.
Robert Sumwalt, a board member for National Transportation, said that the plane's company is developing a "service bulletin". This bulletin is strongly suggesting immediate checks on similar models, the Herald Sun said.
The airline told the Associated Press that 60 other jets should be inspected by late Tuesday.
About 600 flights were cancelled over the weekend, and these cancelations will most likely continue for the inspections, the Star Tribune reported.