Colorado Secretary of State records show the father and son obtained business licenses in August and planned to call their services, "Big Apple Airport Shuttle" and "All Seasons Limo Service."

Najibullah Zazi is accused of trying to create chemical weapons to detonate across New York City on Sept. 11. His father was indicted on Thursday on a charge he lied to federal investigators in a matter involving terrorism.

"This is the kind of job he could have been told to get because it would give you access to airports," Bryan Cunningham, a former federal prosecutor and owner of a corporate homeland security consulting firm, said

Najibullah Zazi's attorney believes his plans to start businesses in Colorado show he and his father were law-abiding citizens.

"I would say that if someone is trying to start a business in the state than they're not trying to flee the area or do any damage to the area," Arthur Folsom, Najibullah Zazi's attorney, said.

The men shopped for a town car and then decided to purchase two SUVs from a dealership in Aurora in August.

The owner, who doesn't want to be named, tells 9Wants to Know the Zazis and another man were at the dealership for about an hour and purchased a 2002 Chevy and 2001 GMC for $12,500 cash.

The father and son and an unknown man also went car shopping at Burt Chevrolet in Denver in August.

At the same time, records show the men were applying for the business licenses.

While Nazibullah and Mohammed Zazi maintain their innocence, Cunningham speculates their actions could have indicated a planned attack at DIA.

"They could have been planning a whole series of things as an alternative to what was going to happen in New York or as a sequential attack," Cunningham said. "The most likely scenario based on this information is that these guys were part of a control cell that was involved in planning and acquiring capabilities to execute a number of different types of attacks and different terrorist missions."

A spokesman at DIA says having a shuttle service to the airport, even with security clearance, does not get drivers any closer to the airport that passenger drivers.

"Taxi and shuttles all sit in the commercial vehicle holding lot, on the east side of in-bound Pena Boulevard until they are called to have access to level 5," DIA spokesman Jeff Green said. "The way we handle ground transport, even with an airport ID badge, only gives them access to get into the commercial holding lot and access to drive up to level 5. That's it."

Mohammed and Najibullah Zazi were both airport shuttle drivers before their arrests. When Najibullah Zazi worked for ABC Shuttle, he passed Transportation Security Administration (TSA) criminal background checks in order to have access to DIA.

Cunningham thinks it's no coincidence the men were shuttle drivers and then tried to open their own shuttle services.

"He may have been sent here by al Qaeda because they already had some infrastructure here or his orders could have been to just go somewhere, not in a huge city where there's a lot of focus on terrorism, and this is the one he picked," Cunningham said.

The first name Mohammed Zazi chose for his business was "Arub Limo Service" which means "loves her husband" in Arabic.

The name was later changed to "All Seasons," according to state records.

If you have any story tips, please email 9Wants to Know Investigator Deborah.Sherman@9NEWS.com.