OTTAWA - The federal languages watchdog will be spending up to $90,000 from the public purse to go undercover at eight airports to check whether air travellers are being served in both English and French.

Starting this fall, Official Language Commissioner Graham Fraser's spies will anonymously verify the level of bilingualism at airports in Halifax, Quebec City, Montreal, Ottawa, Toronto, Winnipeg, Edmonton and Vancouver, and on Air Canada flights.

Fraser, whose mandate ends next October when the report is scheduled to be released, called it his "swan song."

"I've always thought the language rights of the travelling public are extremely important," he said Wednesday.

This won't be the first time Fraser's office probes airports - his office conducted a similar exercise four years ago.

"I thought it would be useful to get an update on how well those airports are doing," he said.

Fraser noted travellers often gripe about the lack of bilingual services they receive in airports, bus and train terminals -- over 10% of the office's complaints are from travellers alone.

Last year, they also received 39 language-related complaints from Air Canada clients. As a former Crown corporation, the airline must comply with the Official Languages Act - and it's been in hot water before. In 2011, an Ottawa-area man successfully sued Air Canada for $12,000 for failing to provide French service on flights he was on.

Karen Selick, litigation director with the Canadian Constitution Foundation, said the probe fell under Fraser's mandate and complied with the act. But she said spending money on enforcing bilingualism nationwide was throwing good money after bad.

"The evidence is anglophones are not becoming bilingual despite what I gather is billions of dollars we've now spent promoting these policies," she said. "And we're just wasting a lot of money."