"We do not tolerate discrimination of any kind and will continue to exhaust our internal investigation until we know the facts of this case and can provide answers for the employees and customers involved in this incident," the airline said in a statement.
"We are always concerned when passengers are inconvenienced and especially concerned when a situation occurs that causes customers to feel their dignity was compromised. We do not tolerate discrimination of any kind."
The men eventually booked a flight on Northwest Airlines to Phoenix, where five of the six clerics live. The other imam is based in Bakersfield, California.
CAIR officials said the convention which the men attended drew about 150 imams from all over the country, and that those attending included Democratic U.S. Rep,-elect Keith Ellison, the first Muslim to be elected to Congress.
Associated Press Writer Jeff Baenen contributed to this story.