Cnn Business reporter Amol Rajan contributed to this report.
By Marta Fields
(CNN) — After the latest dust-up over flying hours, American Airlines has canceled more than 600 additional flights on Sunday.
The airline was set to cancel 550 flights at O’Hare International Airport in Chicago and 60 more at Midway Airport on Sunday, the Chicago Tribune reported.
On Saturday night, United Airlines announced its cancellation of 50 flights. On Sunday morning, American’s cancellation list included 500 additional flights at O’Hare and 50 more flights at Midway, according to the Tribune.
The two airlines together account for nearly 50% of the flights in and out of O’Hare International Airport on an average day, said Joel Nettelfield, a spokesman for Chicago Department of Aviation.
By comparison, United Airlines operates about 33% of the flights in and out of O’Hare on an average day, according to Nettelfield.
A federal government investigation into the pilot scheduling problems at American and United was announced Wednesday. American blamed the problems on its pilot union.
Although pilots at American Airlines typically fly four 12-hour shifts over the course of their eight-day workweek, some have been scheduled for five-day shifts, which can include nighttime flights.
Many pilots have complained that the scheduling decision puts them in a scheduling bind.
In recent days, American has said that pilots make annual salaries ranging from $150,000 to $200,000.
The schedule issues arise at a time when airlines have been fighting for a bigger piece of the lucrative transcontinental traffic.
“The cost-cutting mentality of the last decade continues at American, and unfortunately is largely feeding into issues that I find problematic,” George Hobica, founder of airfarewatchdog.com, told CNNMoney on Wednesday.
Airlines have previously fought with labor unions over who gets to work overnight and on weekends.
Last year, American Airlines pilots approved a new contract that included a clause letting them work four-day workweeks. But that wasn’t enough to meet the needs of the airline’s schedule, and the company says they are still limited in hours.
CNN Business’s Amol Rajan contributed to this report.
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