Claims over market share on the Belfast-Heathrow route has led to an angry exchange between the two competing airlines.

Aer Lingus, which operates from Belfast International, has been accused of "buying market share" after claiming to have taken 42 per cent of the Heathrow traffic.

However, bmi, which operates from George Best Belfast City Airport, described Aer Lingus' claims that it was on its way to taking half the market share on the route as "absurd".

Said Brenda Morgan, bmi's Northern Ireland Sales Manager: "Free seat promotions by Aer Lingus are distorting the market.

"The figure of 42 per cent quoted by Aer Lingus refers to one month only (August), a peak holiday month, when they were running a free seat promotion. So they have in effect been buying market share.

"If things are going so well for Aer Lingus, why is the airline reducing its services to three a day from the start of the winter schedule, October 28, and continuing with just three a day for the summer 2009?

"Bmi will be continuing to invest in the Northern Ireland market and its route to Heathrow, maintaining its eight rotations a day, as well as investing in ground services, providing value for money, and offering competitive fares".

And, referring to a comment by Enda Corneille, Corporate Affairs Director of Aer Lingus, that customers were voting with their feet after years of "being ripped off by bmi", Brenda Morgan declared: "With such comments Aer Lingus are becoming more like Ryanair every day."

The row between the two airlines sparked when an Aer Lingus statement claimed that it had taken 42 per cent of the London Heathrow market in just seven months of operations from its Belfast base at the International Airport.

The airline, which has one third of the total capacity on the Heathrow route, said it was "well on its way to taking half the market share from bmi, which had a monopoly on the service for years until Aer Lingus began flying to Heathrow in January 2008."

Enda Corneille said: "These new figures released by Civil Aviation Authority bring fantastic news for the Northern Ireland holidaymaker and businessman and woman, and of course for the airline.

"It's clear that the marketplace is responding to our low fares and quality service offering by voting with its feet after years of being ripped off by bmi.

"The response from our customers is very encouraging, not alone on our Heathrow service but on all of our routes from Belfast, with performance at the new base more than meeting our expectations.

"Furthermore, we recently recorded our half-a-millionth booking and are on schedule to take more than 700,000 bookings in time for our first anniversary of flying from Northern Ireland on December 10."

Responding, bmi said it did not want to get into a "war of words" with Aer Lingus but it was "not prepared for them to mislead the public by quoting one month's statistics."

Bmi said that according to CAA statistics for Aer Lingus - since start of operation - they currently hold 31 per cent market share on Belfast-Heathrow.

"It is unusual for airlines to quote just one month's statistics. Aer Lingus holds 10 per cent of the total London market as per the CAA stats July YTD (year to date).

"Increases relate to continuous free seat promotion which in effect 'buys market share'. Aer Lingus has been offering free seats with passengers just paying for taxes and charges.

"If you give away seats for free then clearly any airline should be able to fill its seats, however despite their Ryanair tactics and claim that bmi have been 'ripping passengers off' - bmi still retains almost 70 per cent of the market share since Aer Lingus arrived. This proves that the Northern Ireland passengers want the bmi quality of service, the wide choice of departure times and value for money fares!

"Despite Aer Lingus claim that their Belfast base has more than met their expectations, by reducing their flights to three a day it seems they are not prepared to continue their investment at the same level as when they arrived!"