The tax, championed by President Jacques Chirac and backed by UN Secretary General Kofi Annan, adds a surcharge of between one and 40 euros (1.
25 and 50 dollars) depending on the destination and class of seat.
Money raised is to go to an international fund to buy treatments for AIDS, tuberculosis and malaria.
A number of countries -- Brazil, Chile, Cyprus, Congo, Gabon, Ivory Coast, Jordan, Luxembourg, Madagascar, Mauritius, Nicaragua and Norway -- have all signed on to the initiative, and France hopes others will follow suit.
The United States, Canada and Germany, though, oppose the levy, and several airlines have complained that it will simply add to the cost of air travel at a time of high fuel prices.
The money from the tax on flights from France is expected to generate 200 million euros a year for an International Drug Purchase Facility, also known as Unitaid.
The fund will be used to bulk-buy medicines for countries -- mainly in Africa -- that cannot afford them.