The runway will be extended by 500 metres to handle large aircraft.
The 28km road is expected to be ready by Jan 15, 2023.
Angama Airstrip is being converted into an international airport.
The project has a contract sum of $163m (Sh18.7 billion).
The project aims to ease traffic jam on the two roads.
The 9.8km road has been under construction since July 2017.
The government hopes to launch construction works by August.
The upgrade will enable the airport to handle large aircraft such as Boeing 767 and Boeing 467.