Air Force spending around $4M a day in Libya

"The first thing we did" at the onset of the Libyan operation "was start tracking those additional costs," Air Force Secretary Michael Donley told the Senate Appropriations Committee.

The air service has spent $4 million per day, depending on the expenditure of munitions, to pound Libyan leader Moammar Gadhafi's military, Donley said.

Air Force Chief of Staff Gen. Norton Schwartz told the panel the service's costs should grow to about $70 million through the second week of the campaign.

A Pentagon official on Tuesday told The Hill the U.S. military's tab for the opening days of the mission was $550 million. U.S. costs are expected to level out at about $40 million a month, the official added.

Lawmakers from both parties have raised concerns about the costs of the Libyan campaign as Washington wrestles with a fiscal crisis.

Schwartz said costs should come down for the Air Force and the entire U.S. military force should shrink as coalition aircraft take on more sorties, including "strike missions," meaning ones targeting Libyan military platforms and facilities.

In the meantime, after initially predicting the Air Force's prized F-22 fighter would be used "in the early days" of a Libyan operation, Schwartz told the panel the primary reason the Raptor fleet was not used is because there are no F-22s based in Europe or the Middle East.

The decision came because there was an emphasis on setting the operation in motion quickly, and moving F-22s would take longer than using other fighters already nearby, like the F-15, Schwartz said. Donley added that the F-15 is better suited to take out ground targets than the F-22, designed primarily for fighter-on-fighter dog fighting.

This story was updated at 10:55 p.m.