Southwest says the delays are due to inspections of its fleet of roughly 700 Boeing 737s. The inspections began on April 17, the day after an engine broke up and exploded on a flight from New York to Dallas, killing New Mexico resident Jennifer Riordan.
Overall, Southwest ordered 128 flights canceled and 397 delayed throughout the country as of noon Monday, according to Flightstats.com.
The airline would not provide information on cancellations and delays for Monday and the coming week.
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On Friday, the Federal Aviation Administration ordered airlines to inspect the fan blades of CFM56-7B engines, which are used on many 737s, that have been cycled more than 30,000 times.
The engine's manufacturer estimated that the FAA's order would affect 352 engines in the United States and 681 worldwide, the FAA said in a statement.
Most major airlines told the FAA that cancellations would be minimal, FAA spokesman Lynn Lunsford said.
A North Texas aviation expert said the next month to month-and-a-half could be a pain for travelers booked onto Boeing 737 flights.
"You're going to see some disruption in service. It's not going to cause a problem for six months, more like 30 to 45 days," said Dennis Kelly, a retired airline captain and air safety expert from Coppell.
Southwest said Monday that it is on pace to complete inspections within 30 days. The FAA imposed a deadline of 20 days on airlines last Friday.
"(Southwest) is going to pull every mechanic they can off the line to do these inspections," Kelly said. "But you've got to have mechanics checking for other problems as well."
Kelly pointed to the Minimum Equipment Lists airlines use to legally fly planes that have some inoperable parts or systems but are otherwise airworthy.
"An item can be broken and the plane can still fly, but it has to be labeled with a sticker. There's a really good possibility that there will be a number of these planes flying with (inoperable) stickers that wouldn't be without these inspections," Kelly said.
A CFM56-7B inspection should take about four hours, the FAA estimates.
Southwest would not say how many mechanics were working on CFM56-7B inspections at any given time.
A preliminary inspection of the engine that blew up, killing Riordan, found evidence of "metal fatigue."
Neither the FAA nor Southwest would say whether other engines have been reported with metal fatigue or other problems since inspections began last week.
Metal fatigue was also blamed for an engine failure on a 2016 Southwest flight that made a safe emergency landing in Florida.
Almost 1,000 people gathered in Albuquerque, New Mexico, on Sunday to remember Riordan, The Associated Press reported.
This report includes material from the Star-Telegram archives.