An Australian bus operator has stunned his employees by handing out Aus$15 million (US$15.9 million) in thank you bonuses, with workers saying Wednesday they were overwhelmed by his generosity.

Ken Grenda, 79, sold his family-run company after 66 years and decided to put a chunk of the profits into the pockets of his employees for their hard work and loyalty.

Many of his 1,800 workers thought their banks had made an error when they discovered thousands of dollars in their accounts, the Herald Sun reported.

They received an average $8,500 although some got bonuses as high as $100,000.

"A business is only as good as its people, and our people are fantastic," Grenda said.

"This is to recognise that. We have had people here who are second generation, and one fellow in the same job for 52 years."

Vernon Franklin, a driver at the company for five years after moving to Melbourne from India, said he was blown away by the gesture.

"I was overwhelmed with the generosity of Mr Grenda," he told Channel Nine.

"I think we are losing a great man."

Iain Beberidge, who has worked with the Melbourne-based company for 15 years, said the appreciation the employees felt was not all about the money.

"Ken looked after his employees, he treated them like family," he said.

"Every time he comes past the depot, he shakes everyone's hands, and says 'g'day'."

The company has been bought by another transport operator, Ventura, with all staff reportedly keeping their jobs.

[Image via]