Southwest Airlines has reported that it discovered cracks in five of its older 737-300 aircraft after inspecting the planes following an incident last week where a five foot long hole blew open mid-flight on one of its 737-300s Reuters reports.
The cracks were discovered after Southwest elected to ground its fleet of 737-300s in order to further inspect the fuselages of each plane. Southwest will need to make repairs to those five 737s but says that almost all flights are back to normal today after cancelling 650 flights over the past three days.
According to Bloomberg, the Federal Aviation Administration will announce today that 175 older Boeing 737s with more than 30,000 takeoffs and landings will need to be immediately inspected in order to ensure that they are safe to fly.
That same Bloomberg article also notes that the fuselage of the plane in question was inspected as recently as March 29th and that all maintenance records and inspections were up to date.