NEW YORK (Reuters) - More than 1,200 flights have been canceled within, into or out of the U.S. on Sunday, led by cancellations in top carriers Delta Air Lines and United Airlines, according to data tracker FlightAware.com, in the wake of Friday's global cyber outage.

Airlines are struggling to recover from the tech outage that forced multiple carriers to ground flights on Friday.

Delta on Sunday said it had no further comment following an update on Saturday. It said on Saturday that most of its technology systems have been restored, but that it will continue to see cancellations and delays this weekend. It also said it had extended a travel waiver through Sunday for customers.

CNBC reported Sunday that Delta was offering its crews extra pay to staff flights as it recovers from the outage.

United Airlines was not immediately available for comment.

A software update by global cybersecurity company CrowdStrike, one of the largest operators in the industry, triggered the recent systems problems not just for airlines but in other services as well, such as healthcare and banking.