CHICAGO — A Chicago-area man was charged on Monday with attempting to support a foreign terrorist organization after he was arrested on Saturday at O’Hare International Airport on allegations he was on his way to Syria to join the militant group “Islamic State.”

Mohammed Hamzah Khan, 19, of the Chicago suburb of Bolingbrook, appeared before U.S. Magistrate Susan Cox in U.S. District Court in Chicago, and she ordered him held pending a detention hearing on Thursday.

Khan was arrested at the airport after he tried to fly to Istanbul on Austrian Airlines, according to the criminal complaint against him from the U.S. Attorney for the Northern District of Illinois.

Under questioning, he told federal agents he planned to meet a contact in Turkey who would take him to ISIS, or      “Islamic State”, and he expected “to be involved in some type of public service, a police force, humanitarian work, or a combat role.”

In a search of his home, agents found notebooks in which he planned the trip.

Khan also left a note to his family that read in part: “I extend an invitation, to my family, to join me in the Islamic State,” according to the complaint. In the note, Khan wrote that he had an obligation to migrate to territory controlled by the group and he was upset he was obligated to pay taxes that would be used to kill his Muslim brothers and sisters, it said.

U.S. officials say more than 100 citizens have made plans to join extremist fighters in Iraq and Syria. Some have gone and come back while others were caught before their departure in recent stings by federal agents. A small number are either dead or still fighting. FBI Director James Comey estimates roughly a dozen Americans are currently aiding ISIS.

The United States has no specific law preventing individuals from joining such groups, but it has anti-terrorism laws that it has used to prosecute them.

If found guilty of attempting to provide material support to a foreign terrorist organization, Khan could face a maximum of 15 years in prison and a $250,000 fine.

U.S. officials keep a close eye on young people flying to Turkey, which borders Syria, and a red flag in Khan’s case may have been his plans to fly to Istanbul for two nights then return.