BALAD AIR BASE, Iraq - Away from the headlines and debate over the "surge" in U.S. ground troops, the Air Force has quietly built up its hardware inside Iraq, sharply stepped up bombing and laid a foundation for a sustained air campaign in support of American and Iraqi forces.

Squadrons of attack planes have been added to the in-country fleet. The air reconnaissance arm has almost doubled since last year. The powerful B1-B bomber has been recalled to action over Iraq.

The escalation worries some about an increase in "collateral damage," casualties among Iraqi civilians. Air Force generals worry about wear and tear on aging aircraft. But ground commanders clearly like what they see.

"Night before last we had 14 strikes from B-1 bombers. Last night we had 18 strikes by B-1 bombers," Maj. Gen. Rick Lynch said approvingly of air support his 3rd Infantry Division received in a recent offensive south of Baghdad.

Statistics tell the story: Air Force and Navy aircraft dropped 437 bombs and missiles in Iraq in the first six months of 2007, a fivefold increase over the 86 used in the first half of 2006, and three times more than in the second half of 2006, according to Air Force data. In June, bombs dropped at a rate of more than five a day.

Inside spacious, air-conditioned "Kingpin," a new air traffic control center at this huge Air Force hub 50 miles north of Baghdad, the expanded commitment can be seen on the central display screen: Small points of light represent more than 100 aircraft crisscrossing Iraqi air space at any one time.

The increased air activity has paralleled the reinforcement of U.S. ground troops, beginning in February, to try to suppress the insurgency and sectarian violence in the Baghdad region. Simply keeping those 30,000 additional troops supplied has added to demands on the Air Force.

"We're the busiest aerial port in DOD (Department of Defense)," said Col. Dave Reynolds, a mission support commander here. Working 12-hour shifts, his cargo handlers are expected to move 140,000 tons of cargo this year, one-third more than in 2006, he said.

The greatest impact of the "air surge" has come in close air support for Army and Marine operations.

Early this year, with little fanfare, the Air Force sent a squadron of A-10 "Warthog" attack planes — a dozen or more aircraft — to be based at Al-Asad Air Base in western Iraq. At the same time it added a squadron of F-16C Fighting Falcons here at Balad. Although some had flown missions over Iraq from elsewhere in the region, the additions doubled to 50 or more the number of workhorse fighter-bomber jets available at bases inside the country, closer to the action.

The reinforcement involved more than numbers. The new F-16Cs were the first of the advanced "Block 50" version to fly in Iraq, an aircraft whose technology includes a cockpit helmet that enables the pilot to aim his weapons at a target simply by turning his head and looking at it.

The Navy has contributed by stationing a second aircraft carrier in the Persian Gulf, and the reintroduction of B1-Bs has added a close-at-hand "platform" capable of carrying 24 tons of bombs.

Those big bombers were moved last year from distant Diego Garcia in the Indian Ocean to an undisclosed base in the Persian Gulf. Since February, with the ground offensive, they have gone on Iraq bombing runs for the first time since the 2003 invasion.

As chronicled in the Air Force's daily summaries, more and more pilots are getting the "cleared hot" clearance for bombing runs, usually with 500-pound bombs. In recent Army operations north of Baghdad, for example, Air Force planes have struck "factories" for makeshift bombs, weapons caches uncovered by ground troops and, in one instance, "several houses insurgents were using as fire positions."