Earlier in September, Ryanair announced it was offering SAS executives and board members “free tickets on any of Ryanair’s 100 Nordic routes”.

While Ryanair has since rescinded the offer, SAS Director of Communications and Executive VP, Claus Sonberg, remained eager to take up Ryanair’s challenge to “experience how a successful airline operates.”

On Monday, Sonberg boarde a Ryanair flight from the Norwegian capital of Oslo bound for London’s Stansted airport to, as he put it on the SAS Facebook page, “check out how Ryanair really works.”

Throughout the day, as Sonberg published updates of his journey on the SAS Facebook page, he noted a number of unpleasant “surprises” such as charges for baggage and priority boarding.

When all was said and done, Ryanair’s ‘budget’ flight came to 1564 Norwegian kronor ($264), only 354 kronor cheaper than the equivalent SAS flight, an outcome which soured Sonberg on the Ryanair experience.

“A saving of 354NOK does not equate well to all the extra hours of travelling when flying with Ryanair. I had to get up before 6am Oslo time to be in London for a meeting at 1pm, local time,” he wrote on Facebook.

On several occasions, however, Sonberg’s Facebook reports prompted comments which questioned the SAS VP’s account of the trip and directed readers to statements by Ryanair.

The poster of the provocative comments called himself Fletcher Reed, the character played by Jim Carrey in the film ‘Liar, Liar’.

In one comment, ‘Fletcher’ claimed that, on the day that Sonberg’s flight was booked, the SAS price for a flight from Oslo to London had actually reached a whopping 3,344 Norwegian kronor, compared with Ryanair’s modest fee of 970 kronor.

In another, he quoted an entire Ryanair press release, in which spokesperson Stephen McNamara stated that Sonberg had “saved a fortune” by flying with the Irish airline.

Later on Monday, SAS issued a statement which it linked to from its Facebook page accusing Ryanair of employing a “dirty-trick style” in issuing three inaccurate statements about SAS in three months.

Despite the insinuation by SAS that the mysterious Facebook character was planted by the discount Irish airline, Ryanair’s McNamara denies any involvement in the prank.

“I’m sure SAS assumes anyone who says anything positive about Ryanair must be working for the company,” he told The Local on Monday, calling SAS’s “high-price model” a failure.

The spat is just the latest in a long-running feud between the two rivals.

Back in July, claims by Ryanair that it had the best record of punctuality, prompted an SAS spokesperson to refer to the company as the “clowns of the airways”.