Commercial air service at Hilton Head Island Airport could diminish as soon as 2012 if the runway there is not extended, according to a draft released Thursday of the long-awaited airport master plan.
Delta Air Lines will cease use of the turboprop planes it flies into Hilton Head as early as 2012, according to the study.
US Airways also says it plans to phase out its aging turboprop planes but has not announced its replacement aircraft, the study says.
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The recommendation by consulting firm Talbert and Bright remains the same as in earlier versions of the plan -- a runway of 5,400 feet is needed to ensure the future of commercial air service on the island -- and the airlines agree.
"Due to the constraints of runway length and (tree) obstructions ..., the existing airport is marginally adequate for viable service to the Charlotte and Atlanta hubs," according to Talbert and Bright.
The current runway and tree obstructions force the airlines to fly fewer passengers, causing customers to wait for later flights during peak season and service to be less profitable in a slow economy, according to the study.
The airlines fly in and out of Hilton Head 60 percent full, on average, well below the industry standard of 78 percent, according to Talbert and Bright.
For example, Delta's partner, Mesaba Airlines, runs at least three daily flights March through October to Delta's hub in Atlanta using a Saab 340 turboprop plane. The planes can hold 34 passengers, but the airline sells only 21 of those seats because of the weight limit required for the runway.
US Airways provides at least seven daily flights to its hub in Charlotte and one daily flight to Washington, D.C., year-round.
Fuller commercial flights and larger aircraft would serve Hilton Head in the future, but only with a runway of 5,000 to 5,500 feet, according to the airlines.
US Airways and Delta say they will increase passenger numbers and add newer aircraft and more flights, provided the runway is extended at least 700 feet, the study says.
"More than 5,000 feet would be great," Dan Sauter, Mesaba Airlines fleet manager, said Thursday. "That and added clearance from tree removal would eliminate many of the restrictions we have."
The Federal Aviation Administration has said it supports an extension of the 4,300-foot runway to 5,400 feet. A runway shorter than 5,000 feet would result in "rapidly diminishing support" from the FAA, which would pay for 95 percent of the expansion, said Scott Seritt, manager of the FAA's Atlanta Airports District Office.
Talbert & Bright proposes a two-phase extension. The first phase would lengthen the runway 700 feet by extending both ends into grassy safety areas. The second phase would extend it another 400 feet, requiring rerouting part of Beach City Road and the purchase of five parcels around the airport.
Town Council members said they have not yet had time to review the lengthy document released Thursday, and plan to do so during the next few days.
Beaufort County and Hilton Head elected officials are scheduled to meet at 6 p.m. Oct. 27 at Hilton Head Island High School's Visual and Performing Arts Center to discuss the master plan and whether to endorse it.