A Daimler bus, an LVD Convoy and a Taylor transport trailer - with a combined value of almost £45,000 - were completely gutted in the blaze, which broke out at a haulage yard in the Carnanee Road area of Ballyclare at around 11pm on Sunday.
Ben Allen of Allen's Tours says his business is being targeted.
It comes after another bus carrying five tourists had its windows smashed by stone throwers as it passed through the Springfield Road area of west Belfast last week.
"We just have to apologise to the tourists and try to make light of it," said Mr Allen.
Both buses are completely wrecked. There are just the metal frames of the seats left. They are going to have to be scrapped.
"It's going to get to the stage where someone is going to be injured. Also, it is going to put people off coming to Belfast if they hear about something like that."
There have been allegations that social media sites have been used to organise attacks after passengers on board an Allen's Tours bus waved Union flags while passing Belfast City Hall, following a vote to reduce the number of days the flag is flown.
DUP MLA for north Belfast William Humphrey said: "It is utterly appalling and outrageous that a legitimate company, its personnel and its property should be targeted in this way.
"These attacks represent sectarian and political fascism. Those responsible must be condemned by all right-thinking people and all political parties.
"The PSNI must investigate all aspects of this criminal campaign thoroughly, including the threatening comments made on social media."
Police confirmed arson is one line of inquiry into Sunday's incident.