Maher Khalil and Anas Ayyad were told by a gate agent at Midway Airport on Thursday that they wouldn't be allowed on the plane because a fellow passenger had overheard them speaking Arabic - and was afraid to fly with them.

The two friends reportedly of Palestinian origin and in their late 20s were eventually allowed on the Southwest flight but only after being questioned by airport security and police who Khalil told the local NBC television affiliate he had called himself.

Once on board Khalil said some passengers made him open a white box he was carrying - filled it turns out with sweets.

"So I shared my baklava with them" he was quoted as saying.

Southwest Airlines told AFP in a statement the flight "departed a few minutes behind schedule" after airline employees "completed conversations with customers who approached us during the boarding process" without providing more details.

Similar incidents have reportedly taken place on other US domestic flights in the wake of last week's attacks in the French capital that killed 130 people which were claimed by Islamic State extremists.

The group which controls large parts of Syria and Iraq has also threatened attacks in the US including releasing a propaganda video singling out New York.

On Wednesday six men identified by fellow passengers as being of Middle Eastern descent were removed from a Southwest flight bound for Houston at Chicago's Midway after they asked to switch seats causing a commotion the local ABC affiliate reported.

"Our crews were unable to resolve the situation without delaying the flight so we rebooked the customers on a later flight that same day" Southwest said in a statement.