Berkshire Hathaway already owns a stake of about 22 percent in Burlington Northern, and said it will pay US$100 a share for the rest of the company.

The majority of the stock issued in the deal will be Berkshire's “A” shares, but Berkshire's board also approved a 50-for-1 split of its Class B common stock for holders of smaller amounts of Burlington shares who opt for a share exchange rather than cash. Berkshire's Class B shares closed Monday at US$3,265. With the split, each share will be worth US$65.30. Burlington shares closed Monday at US$76.07. The shares shot up over 29 percent to US$98.25 in premarket trading.

The deal has been approved by the boards of both companies. It would be the biggest acquisition ever for Berkshire Hathaway Inc.