British Airways boss Willie Walsh has offered to knee Virgin owner Sir Richard Branson in the groin, and said his rival airline boss lacks "anything that stands out".
Walsh was responding after Branson offered a £1m bet that the BA chief was wrong to doubt the future of Virgin in the airline business.
Rejecting the wager, Walsh said: "I don't have £1m, so a knee in the groin, maybe that would be as painful to him as it might be to me."
He then took another swipe at the Virgin entrepreneur and part-time explorer, claiming his company had achieved little in the sector.
"I just don't see that the guy has anything that stands out in terms of what he has achieved in the industry," the Telegraph reported Walsh as saying.
"I've said it publicly, I don't respect him in the way I respect other people in the industry, and that's a personal view."
Branson had earlier taken to his web blog to vent his opinion after Walsh cast doubt over Virgin's sustainability - the latest in a long line of insults between the two men.
"Let's see how much they believe this. Let them put their money where their mouth is," Branson wrote.
"The last time BA had to make a settlement to me for damages (in part for spreading not dissimilar false rumours) I split the money among our staff.
"Rather than suing them on this occasion, I will pay £1m to their staff if Virgin Atlantic disappears within, say, five years. If not, BA pays our staff £1m."
Earlier this year, Virgin conceded defeat in its attempts to thwart BA's acquisition of domestic airline BMI. Opponents of the deal feared it would give BA too much landing capacity at airports.
Emnity between Virgin and BA stretches all the way back to 1990s, when Virgin won compensation after BA mounted a campaign which employed industrial espionage-style tactics to snatch customers and tar Virgin in the Press.