(CNN) A U.S. Air Force veteran who allegedly tried to join ISIS in Syria but was turned back by Turkish authorities before he could get to the war-torn country entered a not guilty plea to terror-related charges Wednesday in a federal court in New York.

Tairod Nathan Webster Pugh, accused of making the foiled attempt in January, was indicted by a grand jury on charges of trying to give material support to the terror group and obstruction of justice, the U.S. Justice Department said in a two-count indictment announced Tuesday.

Among the evidence, prosecutors allege: Investigators discovered on his laptop computer a letter saying he wanted to "use the talents and skills given to me by Allah to establish and defend the Islamic States," and a chart of crossing points between Turkey and Syria, where ISIS controls some territory.

Pugh, a 47-year-old convert to Islam and a former New Jersey resident who served in the Air Force from 1986 to 1990, was arrested upon his return to the United States in January, the Justice Department said.

"Pugh, an American citizen and former member of our military, allegedly abandoned his allegiance to the United States and sought to provide material support to ISIL," Assistant U.S. Attorney General John Carlin said, using an alternate acronym for the Islamist terror group that controls territory in parts of Iraq and Syria.

At his arraignment Wednesday in U.S. District Court in Brooklyn, Pugh appeared in a black T-shirt and khaki pants and stated his name. He pleaded not guilty through his attorney, Michael Schneider.

A sketch of Tairod Nathan Webster Pugh entering a not guilty plea.

The defendant, a former avionics instrument system specialist in the Air Force, flew from Egypt to Turkey on January 10, weeks after being fired from a Middle East-based job as an airplane mechanic, U.S. authorities allege.

But Turkey denied him entry. In the indictment, U.S. authorities said Turkey was likely suspicious Pugh was headed for Syria.

Instead Turkish officials sent him on a return flight to Egypt, where he was detained. In Egypt, he was carrying multiple electronic devices, "including four USB thumb drives that had been stripped of their plastic casings and an iPod that had been wiped clean of data," the Justice Department said in a statement. Pugh had purposefully tampered with the devices to prevent others from getting access to his electronic media, the indictment said.

Pugh was deported to the United States, where agents with the FBI's Joint Terrorism Task Force obtained a warrant for his devices, including the laptop, the department said.

Investigators found a letter from January addressed to a Misha, whom they believe is his wife, authorities said. In it, the writer says: "I am a (mujahedeen). I am a sword against the oppressor and a shield for the oppressed. I will use the talents and skills given to me by Allah to establish and defend the Islamic States."

In addition to that letter and the Turkey/Syria border chart, agents also found recent Internet searches for information on "borders controlled by Islamic state," as well as "Internet searches for 'Flames of War,' an ISIL propaganda video," and "downloaded videos, including one showing ISIL members executing prisoners," the Justice Department said.

They also found what the government said was another 180 jihadist propaganda videos.

Pugh was arrested in Asbury Park, New Jersey, on January 16.

Pugh's past

While in the Air Force, Pugh was trained in installing and maintaining aircraft engine, navigation and weapons systems, the Justice Department said.

Pugh converted to Islam after moving to San Antonio in 1998, according to the indictment. The indictment said he took a job as a mechanic with American Airlines in or about 2001. The airline has not responded to a request for comment.

In 2001, an American Airlines co-worker alerted the FBI that Pugh "sympathized with Osama bin Laden, felt that the 1998 bombings of U.S. embassies overseas were justified, and expressed anti-American sentiment," the complaint said. One year later, an associate told the FBI that Pugh had expressed interest in traveling to Chechnya to "fight jihad."

Tairod Nathan Webster Pugh served in the U.S. Air Force from 1986 to 1990.

From October 2009 to March 2010, he worked in Iraq as an Army contractor for DynCorp, according to the complaint.

According to Pugh's LinkedIn page, he listed himself as a maintenance manager for Gryphon Airlines, a Kuwait-based charter airline, since September 2014.

But the airline told CNN that Pugh was only under consideration to work for it in 2014.

"In third quarter 2014, Mr. Pugh was under consideration for a future Gryphon project, but did not meet the qualifications," the airline said in a statement. "Gryphon declined to hire Mr. Pugh. Gryphon personnel are cooperating with the authorities."

His last known U.S. address was in Neptune, New Jersey, but he had lived in Egypt for about the last year, the indictment said.

If convicted, Pugh could be sentenced to up to 35 years in prison.