Airlines have grounded more than 3,500 U.S. flights for Wednesday and Thursday as a powerful winter storm gathers from Texas and New Mexico through the Northeast.

About 1,680 flights have been canceled for Wednesday, with another 1,840 for Thursday, according to FlightAware.com. Southwest Airlines Co. already has suspended all flights at St. Louis Lambert International Airport and will do the same at Dallas Love Field on Thursday.

The National Weather Service warned that a “large-scale and massive winter storm” will affect the central, eastern and southern U.S. over the next two to three days.

American Airlines Group Inc. said it has grounded 400 flights for Wednesday and another 600 for Thursday, including service by regional partners. United Airlines Holdings Inc. has scrubbed 450 flights each for Wednesday and Thursday. Southwest canceled 400 for Wednesday. Delta Air Lines Inc. removed 120 from its Wednesday schedule.

A string of severe weather in December and January contributed to the cancellation of 51,571 flights in those months, or about 4% of the total in the U.S., according to FlightAware.