A journalist who has spent the past two years documenting jihadist rebels in Syria says there are between 10,000 and 12,000 foreign fighters active in the country at present.
But filmmaker Bilal Abdul Kareem told ITV News Diplomatic Correspondent John Ray via Skype that the fighters pose no threat to their home countries, and that their prime concern was to topple Assad.
Kareem said it was possible that a small number of the 15,000 - 16,000 or so who have been active in the Syrian conflict may have intentions to "hop on planes and do anti-social things" such as commit terror attacks, but dismissed the new security measures imposed on airports as "scare tactics".
He said the conflict had skilled many men and women from all over the world in the methods of war: fighters with rebel forces would be trained in making their own bombs and rockets, but that did not mean they would use these skills when when they returned home.
He said the evidence showed the vast majority had returned home without incident.
He said the airport security measures may increase fear and distrust and could even risk becoming a self-fulfilling prophecy.
Kareem, who has been filming al-Qaeda linked fighters, Nusra Front, said al-Qaeda and its affiliates were a very large, loosely dispersed organisation, with many different views across ranks and borders.
He said many of the fighters he came across were only focused on ousting Assad, and affiliation to al-Qaeda did not mean the fighters were a real threat to anywhere outside of Syria.