BySuzanne Rowan Kelleher,

Forbes Staff.

The four largest U.S. airlines on Wednesday issued travel advisories ahead of a major snowstorm expected to impact the eastern two-thirds of the country this weekend.

An extremely cold airmass, combined with a frontal zone to its south, will produce a “major winter storm from the Central/Southern Plains to the East Coast beginning Friday and continuing through the weekend,” according to the latest forecast from the National Weather Service (NWS).

Delta Air Lines issued a travel advisory allowing passengers ticketed to fly in or out of 41 airports in a dozen states between Friday through Sunday to rebook for free for travel through next Wednesday.