A US official confirmed the plans after Syria on Monday said it was willing to work with the international community, including Washington, to tackle extremist fighters.
But American officials said they did not plan to ask Damascus for permission for the flights despite Syrian insistence that any military action on its soil must be coordinated in advance.
International concern about IS has been rising after a lightning offensive by the group through parts of Iraq and a string of brutal abuses, including the murder of US journalist James Foley.
The United Nations has accused IS and affiliated groups in Iraq of acts that could amount to crimes against humanity.
Damascus on Monday said for the first time that it was willing to work with the international community, including United States and Britain, to tackle IS and Al-Qaeda's Syrian affiliate Al-Nusra Front.
But Foreign Minister Walid Muallem also made it clear that Syria would not accept unilateral military strikes by United States or any other country.
"Any violation of Syria's sovereignty would be an act of aggression," he said.
There would be "no justification" for strikes on Syrian territory "except in coordination with us to fight terrorism".
Muallem said Syria was seeking cooperation within an international or regional coalition, or at the bilateral level within the framework of a recent UN Security Council resolution targeting IS and Al-Nusra.

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