REFILE-U.S. airlines cancel over 1,200 flights due to massive winter storm

(Corrects typo in headline)

Jan 12 (Reuters) - Airlines in the United States canceled more than 1,200 flights on Friday after a massive winter storm knocked out power and affected businesses in 12 states, with forecast of a brutal freeze over the weekend.

A total of 1,243 flights were cancelled and 514 flights were delayed as of 7.14 a.m. ET, according to flight-tracking website FlightAware.

"We expect some operational challenges due to the weather in the Midwest today and potentially tomorrow due to the winter weather in the region," Delta Air Lines said.

The Federal Aviation Administration had on Thursday on Thursday warned that clouds, snow and windforce could delay flights at certain airports.

United Airlines Holdings led the list of cancellations with 238 flights followed by 215 flights by Southwest Airlines.

It has also canceled some flights through Saturday as it awaits regulatory approvals to resume operating Boeing's 737 MAX 9 jets in the country.

The FAA had on Thursday launched a formal investigation on 737 MAX 9 after a cabin panel blew off an Alaska Airlines flight last week in mid-air, forcing an emergency landing.

(Reporting by Nathan Gomes in Bengaluru; Editing by Arun Koyyur)