City officials said they will be adding about 2,000 feet of taxiway. The project is expected to cost $4 million and city officials recently receive funds from the FAA to pay for most of it.
They said while accidents are not a big problem at the airport, a longer taxiway better reduces the chance of collisions.
"One of the ways to that is by adding or extending taxiways, so you can get aircraft on and off the runway as quickly as possible," Belfast Economic Development Director Thomas Kittredge said.
City officials said construction should be completed by the end of June or July.
They said the taxiway extension has been a plan for the airport for decades and that they are glad it is finally happening.