The Sentinel R-1 air craft departed from RAF Waddington and will operate out of a US base in Senegal.
"We have now decided to deploy Sentinel, a surveillance capability that has proved its worth in Libya and on an ongoing basis for counter-insurgency operations in Afghanistan," said Philip Hammond, the Defence Secretary.
At the outset the French intervention to halt the southern advance of Islamist forces, Britain supplied two C-17 military transport aircraft.
"It suggests our involvement is creeping up and I imagine we will see expanded British involvement in the weeks and months to come."
The use of further transport and surveillance aircraft and then air power would be logical next steps. Britain is also likely to supply dozens of trainers for the Malian military under a European Union scheme due to start next month.
David Cameron has insisted that Britain will not deploy ground troops in Mali. But by warning of a "generational struggle" against al-Qaeda in north and west Africa, he made deeper participation more likely.
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