Aito has uncovered 15 operators thought to be trading illegally.
The association appealed to the trade in Feburary for tip-offs about any operator they believed was trading without financial protection.
Aito membership manager Peter Burgess said agents and operators had reported about 50 companies. This was whittled down to 20 after discounting businesses that were not based in the UK or misreported. And five proved they had financial protection but had not advertised it publicly.
Aito has given the remaining 15 until the end of August to arrange suitable protection, or face being reported to Trading Standards or the Civil Aviation Authority.
Burgess said: “We’re not pursuing operators based abroad, even though they cause problems for our members, as it is difficult enough to get Trading Standards to take action against UK-based firms.
“Some operators held their hands up and said they hadn’t realised they needed protection, so we have given them advice as to where to get it. We will follow it through in a few weeks to see if they have arranged suitable protection.”
However, Burgess is pessimistic about Trading Standards’ ability to act.
He said in 2008 Trading Standards conducted only 100 prosecutions across the whole country, adding: “It is funded by local authorities, whose funding is being squeezed by the government.”
Aito will host its annual conference in Brussels on November 19-22.