40. (1986) Following a productive three days in Abu Dhabi, it’s time to move on to your next assignment in Nairobi, Kenya. There is a once weekly nonstop ABU-NBO flight, but alas, not on the day you need. Thankfully, another airline offers a convenient online connection departing early tomorrow morning and arriving NBO in the early afternoon. The first flight to the connection point makes a single enroute stop, followed by a nonstop into Nairobi. It is the only airline offering an online connection where both flights are aboard vintage four engine jetliners of the same type. As an added bonus, First Class is available on both flights. Airline, routing and equipment please
It's not Saudia, Sudan Airways, Yemenia or Ethiopian, but it is a 707. The intermediate stop is in the country of the national airline involved

Per WHBM: Turkish THY, operating Abu Dhabi-Ankara-Istanbul, thence Istanbul-Nairobi.

Per jrl767: I was also thinking about TK, but we now also know it was an African airline. I can only think of one major city in Somalia (Mogadishu), and I’ve noticed OAG listings for Kampala/Entebbe in Uganda that don’t differentiate two airports. So herewith I’ll offer Egyptair via Sharm el Sheikh (SSH) and Cairo (CAI)

It was neither Turkish THY nor Egyptair, though Egyptair via 707 could've worked if you didn't mind a multi-day layover in Cairo. The airline we're looking for was from Africa and operated both 707s and 720Bs...

As to the intermediate stop, think an airport serving a city that begins with "B". Better consult your atlas... It's surprising where you can land those 707s...