MINNEAPOLIS (AP) - Airlines are rushing to add service to North Dakota to haul in workers drawn by the state's oil boom.

Delta Air Lines Inc. said on Monday that it will add two round-trips a day between Minneapolis and Williston, N.D. And United Airlines is set to add three round-trip flights a day between Denver and Williston in November.

Airports in Minot and Dickinson, N.D. are adding service, too.

North Dakota oil production has more than tripled in the last three years, and it's now the second-biggest oil-producing state, behind Texas. Air traffic has boomed, too, as oil companies fly in workers.

The Williston airport's waiting area doesn't have enough room. Managers plan to add a double-wide trailer to expand the waiting area for passengers.

(Copyright 2012 by The Associated Press.  All Rights Reserved)