Fire crews were called to the site of the Leeds Bradford Airport car boot on Greengates Hill, Otley Old Road, shortly before 11pm on Saturday (Jun 12) after 10 portable toilets were destroyed by fire.
Owner of ServiceLoo Ltd Joe Hemsworth said he believed the loos had been set on fire deliberately.
He said: "Basically, someone has come along and destroyed the portable toilets up there. It was just the toilets, but the fire could have easily spread to the skips next to them which were full, or even the grass because it is very dry.
"Because everybody is very busy at the moment in the industry, I've had to pull some toilets off another job and then I'm going to have to take them back on Monday.
"I don't understand why they've done it. What has anyone gained from this? It's going to cost people financially and its wasted the time of the emergency services.
"We're a small family-run business. It's me and my wife and we also employ family members and friends. We have 250 toilets and it's going to take at least two months to get those toilets back so it's going to have an effect on us."
A spokesman for Yorkshire Fire and Rescue Service confirmed a crew attended the scene on Saturday night.
"A series of portable toilets were alight," he said. "Crews used a hose reel to put the fire out."
West Yorkshire Police were contacted for a comment.