Coastal Aviation is regional airline based at Dar Es Salaam (Tanzania). The airline serves Kigali with daily service from Mwanza,  Arusha city airport, Grumeti, Kogatende, Ndutu, Rubundo, Sasakwa, Seronera and Manyara, with a Cessna Caravan.

Flights leaves Kigali at 6.00 a.m and flies back at Kigali at 17.30 a.m. 

Timetables (PDF) from 16 DEC 2012 to 13 DEC 2013 : HERE

There is no office in Rwanda, but you contact them via their website : http://www.coastal.cc/

Coastal Aviation (Tanzania) links Kigali to Seregenti and Maasai Mara