Almost a decade of sniping between Willie Walsh, boss of British Airways, and Richard Branson at Virgin Atlantic has boiled over when the Dubliner launched an extraordinary attack on his bitter rival, branding his opinions "irrelevant" and saying he had no admiration for the serial entrepreneur.
The latest spat comes after Mr Branson's Virgin Atlantic airline vowed to appeal the European competition regulator's approval of the takeover of BMI by BA-owner International Airlines Group, for £172.5m (e210m). Branson claims the deal will "cut consumer choice and screw the travelling public".
Virgin says BA's acquisition of small rival bmi will "cause serious competitive harm at Heathrow" and give Mr Walsh's company "total market dominance".
But at the World Travel & Tourism Council conference in Tokyo, Mr Walsh said: "I'm not surprised [by Branson's objections]; I'd be surprised if he hadn't done it.
"But what he says is largely irrelevant as we have the approval and we're not in any way going to be distracted by anything Branson says."
Mr Walsh rejected claims that there is personal animosity between the pair, having only met him on "two or three occasions." However, he also dismissed Mr Branson's achievements with Virgin Atlantic: "I'm not one of his admirers. I don't see him as someone who deserves my admiration, other people have done more in the airline industry."
The pair's feud kicked off in 2006, when a tip-off from Virgin led to US and UK competition authorities investigating British Airways for alleged price-fixing. Virgin escaped without penalty for blowing the whistle, whilst BA was fined £271.5m (e331m).
Speaking of the case, Mr Walsh said of Mr Branson: "I wouldn't forgive anybody for what they did there."
Asked if he did not like the entrepreneur, he responded: "I've made no secret of the fact. I don't think he likes me either." He said he did not see "any value in the Virgin brand. It's not a global brand".
In the wake of the price-fixing scandal, Mr Branson claimed to have discussed price-fixing during an edition of the BBC's Money Programme. Mr Walsh disputed this, saying "I still cannot recall 'Honest' Richard Branson giving any personal interviews about the issue." But Mr Branson responded: "It is no wonder that BA is in the state it is in if Willie Walsh has the time to watch past editions of the Money Programme."
The duo's bad blood erupted again in 2008, when the Irishman accused Sir Richard of sounding like a "cracked record" over his continuing opposition to BA's transatlantic tie-up with American Airlines and Virgin's "No Way BA/AA" campaign.
He said: "I've heard it all before. The times have changed and I suggest he moves with them as well." BA later won approval for that deal.
The dispute intensified that year over the botched opening of Heathrow's Terminal Five. Mr Branson claimed that Virgin Atlantic had enjoyed a strong start to its financial year thanks to "ongoing" problems at T5. BA responded by saying the terminal was functioning well and it was "not surprising if other airlines are envious".
The only area on which Mr Branson and Mr Walsh are in agreement is in their mutual attack on the UK coalition government's decision to increase air passenger duty by 8pc this month.