Aditya Singh, 36, was arrested on Saturday after airline staff asked him to produce his identification.
He pointed to a badge, but it allegedly belonged to an operations manager who reported it missing in October.
Police say Mr Singh arrived on a flight from Los Angeles to O'Hare International Airport on 19 October.
He reportedly found the staff badge in the airport and was "scared to go home due to Covid", Assistant State Attorney Kathleen Hagerty said, according to the Chicago Tribune.
