The Air Force's AC-130 gunships are among the most powerful weapons in the Pentagon arsenal. But for 50 years the flying service's gunships – lumbering, propeller-driven transports bristling with high-tech sensors and batteries of side-firing cannons – flew only at night in order to avoid enemy air defenses.

Not anymore. New weapons and sensors are freeing the expanding Air Force gunship fleet to fly and fight in daytime, heralding far-reaching changes in U.S. air power. But how far-reaching depends on the willingness of commanders to use the improved, more flexible warplanes, says one ex-gunship pilot.

"They are currently flying during the day," Air Force Special Operations Command chief Lt. Gen. Eric E. Fiel said of his AC-130s at a recent industry conference.

The potential impact of the flight expansion, which had been anticipated for more than a year, is hard to overestimate. AC-130s fly longer, carry more weaponry and fire more precisely than most other planes. "Gunships are in a class all by themselves when it comes to close air support," Bob Seifert, a former AC-130 pilot who flew combat missions over Iraq, tells Danger Room. In adding daytime missions "you've literally increased your overall effectiveness by 100 percent," Seifert points out.

In part because it flew during daylight, a single Marine Corps KC-130 tanker with bolt-on Hellfire and Griffin missile launchers – a sort of half-gunship codenamed "Harvest Hawk" – flew 8 to 10 percent of all close-air-support missions over southern Afghanistan last year, according to Lt. Col. Charles Moses, who commanded the KC-130 squadron. That's "a significant number considering it’s only a single aircraft,” Moses said.

At any given moment around half of the Air Force's roughly 30 AC-130s are deployed to Afghanistan, the Horn of Africa or other conflict zones. If one Marine Harvest Hawk can handle a tenth of all air strikes in southern Afghanistan, imagine what 15 of the more sophisticated Air Force models can do flying around the clock.

Still, the change surely evokes some unpleasant memories within the Air Force. During the 1991 Gulf War, an AC-130 lingered too long during a night mission over the besieged Saudi town of Khafji. The sun came up and Iraqi soldier fired an SA-7 missile, destroying the gunship and killing its 14 crew. "Gunships were vulnerable in the day because they were too slow and predictable for as close as they needed to be to the target," Seifert says.

Times and technology have changed. Fiel cited new sensors being retrofitted to the 1990s-vintage AC-130Us plus improved gear installed from the outset on new AC-130W and AC-130J gunships still rolling off the Lockheed Martin assembly line in Georgia at a cost of $200 million apiece. The new sensors on the AC-130U include a large-aperture midwave infrared sensor, two image-intensified television cameras, a near-infrared laser pointer and a laser designator and rangefinder. By contrast, the earliest AC-130As that flew over Vietnam in the 1960s had only a rudimentary low-light television camera and the pilot's eyes for aiming.

All this new equipment "allow[s] us a longer standoff range" away from enemy defenses, Fiel said. But the greater range "caused a little problem," he admitted. The standard battery of gunship weaponry – specifically, their 25-millimeter cannons – can't reach as far as the sensors can see. To close that gap, the Air Force has added gliding Small Diameter Bombs to the AC-130Ws and is also planning to test out Hellfire missiles, a type of munition already used by Marine Harvest Hawks.

To take advantage of the new sensors, weapons and flight schedule, Seifert has argued that gunships shouldn't be constrained by pre-planned missions. "This method of employment does not fully exploit the great potential of the AC–130 to hunt and kill insurgents," Seifert wrote in a 2007 article for Joint Forces Quarterly. He said the gunships should be allowed to roam the battlefield, striking any enemy targets that appear.

Most importantly, there should be more AC-130s, Seifert tells Danger Room. "To improve the effectiveness of gunships, you simply need to have more of them. A ground force supported by a gunship is near invincible."

But the gunships themselves are not invincible. And the Air Force is only gradually lengthening their safety tether.