Have you looked at LA to DC (IAD), then IAD to Addis to JRO, all with Ethiopian from IAD? They (EA) have some good fares and arriving in the early afternoon in JRO, as opposed to night time, is an added bonus.

Besides Ethiopian/ET out of IAD (Washington,DC/Dulles), recently Qatar Air via Doha and Turkish Air via Istanbul, have started flying into JRO. Not sure from where you can connect in States to Qatar, but know they arrive JRO about 10am; Turkish Air, likewise not sure where you can connect to them, but they do arrive JRO early morning, about 3am.
Now with three more carriers other than KLM, the fares on these new ones might ALL be more competitive.
Check them out.

Flights arrive at Kilimanjaro/JRO Tanzania - the international airport for Immigration/Visas. There is NO international airport at Arusha which is a town about 1/hrs drive west from where safaris start.

If you instead fly into NBO, then there's the Shuttle Bus, departing 8am or 2pm, 5/hrs drive to Arusha... fare about $30-35/pp each way. Departing buses from Arusha are also 8am and 2pm and will go direct to the NBO airport for homebound.

Good luck!

I second Sandi's suggestion, to check out the other carriers. You can do this on www.kayak.com. Ethiopian usually has fairly competitive rates. I flew both Ethiopian and Turkish Air last year and had no problems in either Addis Ababa or Istanbul. You might find that it's no more expensive to go directly to Arusha (JRO) than going to NBO and paying for the transfers to Arusha (not to mention a transit visa for Kenya.)

... and, oh how could I forget? If transiting shuttle bus (land) via Kenya, you will require the Yellow Fever inoculation and proof of same for entry to Tanzania.

Try KLM

wildlifepainter -

KLM we know, but they're the very expensive carrier, why the OP is asking for alternatives.

KLM has flights from LAX via AMS to JRO for $1360, at the end of may, check various days.

I'm meeting three friends from LA in Amsterdam to go down to JRO from there. In Feb their air is $1900 on KLM. LAX-AMS-JRO

On ticketpiolet.com fares in Feb from LAX to JRO range from 1360 to over 3100, again check various days, the difference can be very great.

OK Thanks for all of the great suggestions! Here is what we ended up with: I got two tickets RT LAX/A'DAM/Nairobi nice direct flights, all on KLM (could have saved a few $$ if some of the connections were on Kenya Airways but KA got some pretty lousy reviews so I gave that a pass) RT was $1700 PP which includes taxes etc. We have some time so are going to travel overland Nairobi to Arusha on one of the daily shuttles. This gives us a few days in Nairobi where I haven't been since 2002! So all in all, booked and under budget. Thanks so much!