This operator can help select your international flights, but you'll have to book them yourself help
Fly to/from Kilimanjaro Airport (JRO - Check price) near Arusha. Or fly to/from Arusha Airport (ARK - Check price) via Dar es Salaam or Nairobi (Kenya)
A transfer from and back to the airport can be arranged for an extra cost
Additional accommodation before and at the end of the tour can be arranged for an extra cost
I recommend this agency to everyone and especially to the Spanish-speaking community because you can live a pure experience with the Masaai community, away from mass tourism and "tourism of seeing quickly, buying something, taking a photo...