The Air Force is falling short of the C-17 cargo plane training it needs in Hawai'i for combat landings and takeoff practice and low-altitude terrain flying, an official said.

Already, an approximately 4,200-foot "assault landing zone" planned at Kona International Airport is at least two years late as a result of a budget crunch.

Air Force officials hope the 2009 Pentagon budget will include money for the $28 million practice strip.

The Air Force said it wants to incorporate low-level flying down to 300 feet over unpopulated areas of the Big Island, and at 2,000 feet over populated areas.

"Flying low and using mountains and ridge lines to keep us away from the threat is one of the tactics that we use in this (the C-17) aircraft, and we practice it everywhere except in Hawai'i," said Col. Andy Hockman, the 15th Operations Group commander at Hickam Air Force Base.

The last of eight C-17 Globemaster IIIs assigned to Hickam arrived in July 2006. The active-duty Air Force and Hawai'i Air National Guard jointly operate and maintain the four-engine cargo jets.

The proposed training route over the Big Island avoids Captain Cook, Ocean View and Hawai'i Volcanoes National Park, the Air Force said.

But early information on the plan, which is expected to be detailed in a draft environmental assessment, caused concern that there would be flights over populated areas.

Efforts are being made to reach out to community officials, but the Air Force said it's too soon to talk publicly about specifics.

"Right now, there are a lot of folks very afraid of what we're going to do," Hockman said. "I think we're going to provide some information that hopefully will get rid of some of that."

The C-17 "military training route" corridor would reduce the area where the aircraft operate from 14,400 square miles to less than 500 square miles, the Air Force said.

The flying corridor would be 4 to seven miles wide and approximately 70 miles long "while avoiding populated and noise-sensitive areas," the Air Force said.

Among the areas where low-altitude navigation would take place is Pohakuloa Training Area. The open air space is based on visual flight rules, and the C-17 pilots need to be able to fly under instrument flight rules as well, officials said.

As for combat landings and takeoffs, Hockman said C-17 pilots mainly practice the short-distance maneuvers at the Marine Corps base at Kane'ohe Bay.

A stripe has been painted at 3,500 feet so pilots can practice in the shortened space they need for combat landings.

Hockman said as a result, pilots don't need to be as precise as they would be in a real-world situation.

"As naval aviators practice to land on an aircraft carrier, they learn to fly airplanes on a normal runway, then they fly into a painted zone on a runway, and then they graduate to an aircraft carrier where they've actually got to do it right," he said. "If we don't take it to the next level, then we are not practicing."

In a hostile environment, there may not be the opportunity to "go around, try it again," Hockman said. "In the combat zone, you've got to do it right the first time."

Every six months, seasoned pilots are required to do four daytime combat landing and takeoff operations, while co-pilots and individuals who fly less have to do eight per month.

The maneuvers can't be done at Honolulu International Airport because it is too busy, and the 5,000-foot runway on Lana'i can't handle hard-impact landings.

The $28 million assault landing zone on the Big Island would be built makai of the existing runway and could be used by the state as a taxiway when not in use for C-17 training, the Air Force said.