“President Kenyatta wishes to reassure the entire aviation industry, investors, local and international travellers that everything is being done to resume normal operations,” presidential spokesman Manoah Esipisu said.
A third of Europe’s flower imports, and many fresh vegetables, also come from Kenya.
“This is disastrous,” Jane Ngige, chief executive officer of the exporters association, Kenya Flower Council, told Reuters.
Shares in Kenya Airways, which uses the airport as its main hub, fell 2% after the fire.
Foreign airlines which use the terminal include British Airways, Emirates, Qatar Airways, KLM, Turkish Airways, South African Airways and Ethiopian Airways. Several cancelled flights to Nairobi on Wednesday.
Kenya Airways said flights from London and Bangkok would land as scheduled in Nairobi on Thursday morning, according to Reuters.
British Airways said it was in contact with the authorities to provide customers due to travel with as much information and notice as possible.