Airport officials said the construction was planned before the Aug. 27 crash that killed 49 people and left the plane's co-pilot, James Polehinke, with life-threatening injuries.
The project includes building a new taxiway connection to the airport's main 7,000-foot runway and demolishing a short taxiway connection.
An old taxiway connection to Runway 22 will also be demolished. It was closed the week before the crash when the main runway was shifted to the southwest and repaved.
Runway 26, the shorter, general aviation strip that was mistakenly used by Flight 5191, will remain closed for about 90 days. The 3,500-foot runway has been closed since the crash.
On Sunday night, mourners gathered at Lexington's Rupp Arena to remember those who died in the crash. Eva Ayer was among the hundreds of people who gathered at the arena. Her co-worker, Fenton Dawson, was one of the victims.
"It's like our own little, mini-9/11," Ayer said. "Everyone has really come together."
Lexington Mayor Teresa Isaac, Gov. Ernie Fletcher and pop star Brian Littrell helped lead the memorial attended by several of the victims' families and friends.
"It reminds us of the uncertainty of life," Fletcher said. "Tragedy stopped them short of their dreams and aspirations ... loved ones felt a loss that we can't explain or describe."
Two local choirs led the gatherers in singing "My Old Kentucky Home" and "Amazing Grace." Littrell, a former member of the Backstreet Boys, sang his own song, "Gone Without Goodbye," about people who have lost loved ones in a tragedy.
The Aug. 27 regional jet crash was the worst American plane disaster in nearly five years.
Federal investigators said the flight's captain, Jeffrey Clay, taxied the plane onto the wrong runway before Polehinke took over and attempted to get it airborne from the too-short runway at Lexington's Blue Grass Airport.
The plane crashed and caught fire in a nearby field. Polehinke was pulled to safety from the broken cockpit, but everyone else aboard the plane died in the crash and fire.
Polehinke is now off a ventilator but could be hospitalized for several more weeks with facial and spine fractures, a broken leg, foot and hand, three broken ribs, a broken breastbone and a collapsed lung.
Investigators are looking into airport construction and staffing at the control tower, among other things, as possible contributing factors to the Aug. 27 crash.