The fire forced the cancellation or diversion of scores of flights at east Africa's biggest transport hub.
Using the domestic terminal for passengers instead of the fire-damaged international hall, flights from London and Bangkok safely landed early today morning, said Eric Kiraithe, head of security at Jomo Kenyatta International Airport (JKIA).
"We have received two flights from London and Bangkok, and currently we are checking in passengers flying to other destinations including Zanzibar, Johannesburg and Paris," Kiraithe said.
"We are confident we will process other flights in the course of the day, although we are not fully operational," Kiraithe said.
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Cargo and domestic flights out of the Kenyan capital had already resumed yesterday evening.
However, it was not clear when airlines other than the national carrier Kenya Airways would also land at Nairobi.
The fierce fire, which started before dawn yesterday, took around four hours to bring under control, with firefighters hampered by a lack of both water and equipment.
Some 16,000 passengers usually transit through JKIA every day, according to official figures.
The airport is a regional hub for east Africa, with many long-distance international flights landing there to connect to countries across the region.
There were no casualties in the fire but two people -- an airport worker and a passenger -- were taken to hospital due to smoke inhalation.
August is one of Kenya's busiest months for tourism, a key industry for the country, as foreign travellers fly in to see its wildlife and enjoy the white sand beaches on its Indian Ocean coast.