Buffalo Airways was in court Friday on charges of hauling diesel fuel in oversized tanks without proper certification and dangerous goods markings.

Buffalo Airways has pleaded guilty to the charges under the Transportation of Dangerous Goods Act, which date to March 2012.

The crown says the tanks are unsafe and Buffalo flouted regulations. The Crown asked the judge to fine the airline $200,000. 

Buffalo says the tanks have been in use for 30 years, and while it didn't have certification in this case, it does have an exemption to use the tanks in one of its aircraft.

Buffalo says when the tanks are connected to the fuel system of an aircraft, they no longer require the dangerous goods certification so the issue is not about safety, but more about paperwork.

A decision is expected Aug. 22.