American Airlines cancelled 570 flights on Friday, setting up US airports for a fourth day of chaos and bringing the number of flights cancelled by the carrier this week to more than 3000.

The cancellations, coming after 900 on Thursday, brought further chaos to US airports, as AA raced to perform safety checks. The cancellations came after Delta Air Lines, United Airlines and US Airways pulled flights after officials announced spot inspections of all US airlines’ safety paperwork.