The military said the crash happened at about 2:15 a.m. local time and it "does not appear to be by enemy action." No precise location was given.
Iraqi officials said the crash site was located about 20 miles west of Kirkuk, which is about 180 miles north of Baghdad. They spoke on condition of anonymity because they were not supposed to release the information.
The deaths raised to at least 4,236 the number of U.S. servicemembers who have died in the Iraq war since it began in March 2003, according to an Associated Press count.