Simply revenue raising to offset losses. Think Trading Standards should take a look at this.
This is what Blackpool Airport say they have spent ADF income on to date:
What has the Airport Development Fee money been spent on?
The funds from the ADF have contributed to necessary infrastructure development which has included an upgrade to the taxi-way and runways, extensions to the car parks, improvements to security, new fire and operations centre and is used to develop new route opportunities and fund the free passenger parking offer.
It is difficult to think that Trading Standards would have any interest in it.