Swift Transportation Inc. (NYSE: SWFT) and Knight Transportation (NYSE: KNX) are merging in a $6 billion deal involving two of the largest trucking companies in the U.S.

Both Swift and Knight are based in Phoenix.

The combined companies will have $5 billion in revenue, 28,000 employees, 23,000 tractors and 77,000 trailers. They will stay based in Phoenix.

Both companies saw their stocks jump on the merger news Monday morning. Swift (SWFT) is up almost 24 percent gaining $4.78 and trading at $24.80,…