The regulator of the aviation industry says the safety of commercial ballooning has improved dramatically since January's fatal crash in Wairarapa.

Eleven people died in the January 7 crash in Carterton, 15km southwest of Masterton, after a balloon tangled in power lines and caught fire.

An interim report from the Transport Accident Investigation Commission (TAIC) released on Thursday said the pilot had tested positive for cannabis.

The overall regulation of commercial ballooning is one topic TAIC will be looking at as it attempts to discover what caused the crash, and Civil Aviation Authority (CAA) director Graeme Harris says the industry is now better regulated.

"Since the accident, the rules covering the commercial ballooning sector have changed dramatically, allowing closer oversight by the CAA, and demanding higher standards from operators who wish to carry fare-paying passengers," Mr Harris said.

"To date two ballooning companies have achieved this new certification, and two other companies are working towards it."

TAIC in February urged the CAA to investigate maintenance across the sector after it found anomalies in the maintenance of the crashed balloon, though it said it was too early to tell if the anomalies contributed to the crash.

Mr Harris said it found maintenance practices were, in all but one case, either at or above the required level.

It found administrative and record-keeping issues with the engineer who worked on the Carterton balloon and he will be subject to ongoing audit and inspection.

"At the same time, the 16 balloons that had been worked on by the engineer were rechecked. All were found to be airworthy."

Mr Harris said he was very disappointed in the positive drug test and the CAA was planning an education and safety promotion campaign.