Shares of Boeing Co gained 4 percent in premarket trade on Friday after the company won a $30 billion contract for 179 new U.S. Air Force refueling planes a day earlier.

The win for Boeing came as a surprise to many industry watchers who expected rival EADS to win the contract.

Boeing shares traded at $73.66, up from a closing price of $70.76 on Thursday, but equity analysts have predicted a muted impact on the stock.

"Although we don't expect any short-term financial implications from the Boeing tanker win, as Airbus has 30 days to file a protest and the first aircraft are not expected to be delivered until 2017, this is good news and is widely being interpreted as so. As a result we expect the stock to be up today," said Alex Hamilton, managing director of EarlyBirdCapital.

Boeing's business is split between defense and commercial airplane products, and its shares more closely track developments in commercial orders and deliveries.

RBC Capital Markets analyst Robert Stallard said in a research note late on Thursday that he expects "little near term impact on Boeing's earnings in 2011."

"...the company has already factored in some spending related to winning the tanker program in its guidance," he said.

Boeing has given no details on pricing of the contracts, but some experts believe Boeing kept margins tight to keep its bid low.

(Reporting by Kyle Peterson, editing by Dave Zimmerman)