As officials continue to investigate a hot air balloon crash that claimed 16 lives in Lockhart, Texas Saturday, emerging details about the deceased pilot's past are raising questions about the Federal Aviation Administration's oversight of balloon operators.

The Associated Press reported Tuesday that 49-year-old Alfred "Skip" Nichols, owner of Heart of Texas Hot Air Balloon Rides, was convicted of driving under the influence four times between 1990 (six years prior to his obtaining a balloon pilot's license) and 2010 in Missouri.

Nichols was also convicted of a drug crime in 2000, for which he served around a year and a half in prison before being paroled. He returned to prison in April of 2010 after his parole was revoked as a result of his DUI conviction that year, and was paroled again in January of 2012.

While there is absolutely no evidence that Nichols had been drinking or was otherwise impaired when the balloon went down on the morning of July 30 (an ex-girlfriend told the AP he'd been sober for four years), some say revelations about the pilot's past - including crash landings in Missouri in 2009 and 2013, as well as a crash landing in Katy, Texas in August of 2014 - indicate a major gap between FAA standards for balloon operators versus plane and helicopter pilots.

Airline captain and aviation safety consultant John Gadzinski told the AP the FAA might allow a recovering alcoholic to fly commercial aircraft if the pilot could prove they were undergoing successful treatment, but that the agency is unlikely to accept an airline pilot with DUI convictions.

Robert Sumwalt, a member of the National Transportation Safety Board and former airline pilot, told the AP he was required to submit FAA medical paperwork every six months.

However, according to Patrick Cannon with the Balloon Federation of America, balloonists are able to submit a statement from a doctor that does not require them to disclose any past substance abuse convictions as they would when turning in FAA forms.

Current FAA regulations do not require balloon pilots to hold a medical certificate of any class, and only sport pilots are required to at least have a driver's license. Applicants are asked to certify that they do not know or have reason to know of any medical condition that would render them unable to operate a balloon in a safe manner, though the FAA's website does not specify how.

The push to hold balloon operators to standards on par with other aircraft pilots is not new.

In a letter to FAA Administrator Michael P. Huerta dated April 7, 2014, NTSB Chairwoman Deborah A.P. Hersman cited several hard landings made by balloon pilots and wrote the following:

These accidents highlight operational deficiencies in commercial air tour balloon operations, such as operating in unfavorable wind conditions and failure to follow flight manual procedures, that the NTSB is concerned are a result of the  current lack of oversight relative to similar airplane and helicopter air tour operations.

The NTSB concludes that passengers who hire air tour balloon operators should have the benefit of a similar level of safety oversight as passengers of air tour airplane and helicopter operations.

The FAA rejected the NTSB recommendations, and said they would not result in significantly higher operational safety since ballooning is not as common as airplane and helicopter operation.

Responding to Hersman, Huerta wrote, "The FAA believes the risk posed to all pilots and participants is also low given that ballooners understand the risks and general hazards associated with this activity".

16 people, including Nichols, were killed Saturday, August 30 when a hot air balloon piloted by Nichols crashed in a Lockhart, Texas field, about 30 miles southeast of Austin.

Investigators were still working to determine the cause of the crash Tuesday morning. The balloon ran into high-tension power lines prior to crashing, but it remains unclear whether that caused the crash or if the balloon was already aflame before colliding with the lines.

Electronics including cameras, tablets, and smartphones were sent to a lab to determine if any information can be salvaged from them. The balloon was transported to a secure facility in Dallas.

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