Flying from the Americas
The number of possibilities is more limited than flying from Europe, but still you will be able to find a couple of airlines flying you to Madagascar.
If you fly from the Eastern coast of USA or Canada probably the best option would be to take a South African Airways flight to Johannesburg, which would cost you around 1.300 US$. South African Airlines offers direct flights to South Africa from New York and Washington. To get there, you can book an internal flight with United Airlines to Washington from all major US and Canadian cities. At the United Airlines site you can enter your departure city and destination (Johannesburg) and all journeys will be issued in the same tickets. After arriving at Johannesburg you might need to overnight at an airport hotel (we would not recommend spending the night at the airport itself) before taking the connecting flight to Tana with Air Madagascar (on Mondays, Wednesdays, Thursdays, Fridays, Saturdays and Sundays) The approximate return price for this connection flight would be around 650 US$. Check the valid schedules of both airlines at: www.flysaa.com and www.airmadagascar.com.
If you fly from the Western coast of USA or Canada, getting to
Washington could be just too expensive. In this case flying over Asia
can result more affordable. You can fly to Bangkok with any cheap Asian
airline and then take the Air Madagascar connection flight to
Antananarivo which connects Bangkok with Madagascar’s capital
Reunion on Tuesdays and Saturdays (according to the current schedule).
It goes back to Bangkok on Mondays and Fridays. A flight ticket for
this journey can cost you about 1.000 US$. Getting to Bangkok is a
simple thing and there are numerous airlines flying from USA and Canada
to Thailand like Thai Airways (direct flights from Los Angeles),
Singapore and Malaysian Airlines (both latter via Singapore / Kuala
Lumpur from lots of North American airports). Calculate further 1.000
US$ for it (or less if you are able to find an internet deal).
If you are flying from South America connections are much more difficult. South African Airlines flies from Sao Paulo to Johannesburg, where you can get from any bigger airport in South America. Expect to pay between 300 and 600 USD (depending where you are flying from) for a return ticket to Sao Paolo. From Johannesburg you can fly to Tana with Air Madagascar (see above).
But of course you can opt to fly via Europe. The number of airlines connecting numerous North and South American airports with Paris is extraordinary high, so that we will not reflect them here. From Paris you can fly to Tana with Corsair, Air Madagscar and Air France (see under point flying from Europe).