Traffic along the H-1 freeway has been generating some additional noise complaints — from an altitude of about 1,000 to 2,000 feet.

Army UH-60 Black Hawk helicopters have been ferrying troops and supplies back and forth to Pohakuloa Training Area on the Big Island as Schofield Barracks’ 25th Combat Aviation Brigade trains for a January deployment to southern Afghanistan.

Groups of about four of the choppers regularly fly south from Wheeler Army Airfield and hang a left at H-1, making what is known as the transition through Honolulu Airport’s "Class B" airspace, officials said. They fly the reverse route on the way back.

"That is the same transition that civilian small private airplanes are required to use, and that we are required to use," said Col. Frank Tate, who commands the aviation brigade. "The transition through Class B airspace is absolutely at the discretion of the air traffic control folks, so they give us our clearances."

Koko Head has a directional beacon and is used for routing, and H-1 becomes a two-way freeway in the sky.

The Army ramped up deployment training in about mid-February for the Black Hawk flights, which are referred to as the "Lightning Express," a reference to the 25th Infantry Division’s Tropic Lightning nickname.

Residents in Makiki and Kaimuki in particular have been registering some complaints over the noise. The helicopters don’t fly precisely over H-1, and westbound air traffic can be closer to residences because of their higher hillside elevation. Cloud cover can also mean lower-altitude flights, officials said.

"The noise is excessive," said Makiki resident Sam Buris. "They have said they are working on it, but it hasn’t stopped."

The office of state Sen. Les Ihara Jr., whose district includes Maunalani Heights and Kaimuki, sent e-mails to 75 to 100 residents explaining the training. Ihara said he thinks the best solution is to have the helicopters take a different route.

Ihara’s office manager, Heather Bolan, said she received mixed feedback to the e-mail. Some said it was the first time they had heard the Army helicopter noise so frequently, and sometimes early in the morning, she said.

"Some others are like, ‘Well, we are at war. If this is the price we have to pay, it’s not really that upsetting,’ " Bolan said.

Tate said he’s aware of the noise concerns, and he’s working with the Federal Aviation Administration and air traffic control to see if alternative routes can be used.

One route the Army has asked for would take the choppers through Honolulu Airport and out to sea, but that would place the Army aircraft in the same airspace as jetliners, which "makes them a little bit nervous," Tate said.

Tate said the FAA and air traffic control officials have been "very cooperative," and he’s expecting an answer on possible alternative routes within the next two weeks.

The frequent Black Hawk flights to Pohakuloa for this training iteration will end in about a week and a half, he said. Training flights for larger CH-47 Chinook helicopters are expected to start around mid-August.