Deregulation, competition and the arrival of low-cost airlines permitting anybody to fly anywhere in the world for less than a week's wages, have seen their status slip sharply to the point where Dart train drivers last year argued for a pay increase based on parity with airline pilots.

The pilots' union, Ialpa, which is now a part of the public service union, Impact, realises that if left unchallenged, the former national carrier's move to recruit pilots in Belfast on inferior terms and conditions will spread throughout the company. That is why the pilots decided they must make a stand now against the recruitment of 'yellow pack' pilots in Belfast.

But within the company it is a lonely stance.

Up to the end of the week, Siptu's silence on the pilots' action was deafening. While few in Siptu would ever listen to Michael O'Leary, some Siptu heads were quietly nodding when the Ryanair boss described the Aer Lingus pilots as "overpaid peacocks".

Aer Lingus pilots are on a starting salary of around 70,000 a year for a co-pilot. This rises to 180,000 for an experienced captain. Under EU safety regulations they can fly only a maximum of 900 hours in the year, the equivalent of 17 hours a week. In practice, due to the roster system, many Aer Lingus pilots fly less than that. While Aer Lingus has been less than clear about the terms and conditions in Belfast, the company mentioned a salary of 113,000, and a lesser pension scheme. All Belfast pilots will work the full 900 hours.

The former state airline has been riven with inter-union warfare ever since Siptu accused Impact of poaching its cabin crew members, something which severely dented its power base in the former state airline.

The fact that most of the 1,500 cabin crew were happy enough to quit Siptu and join the union that represents pilots created a class divide in Aer Lingus between those working in the sky and the lesser mortals beavering away on the ground.

This bitter poaching row between two of the country's biggest unions went on for years and at one stage almost sank the prospects of a national wage agreement.

While Impact and Siptu have since signed a co-operation agreement at national level, the row lingers in Aer Lingus, where Siptu ground staff believe pilots and now cabin staff are pursuing their own agenda at the expense of other workers.

Last year the pilots again went out on a limb when they privately tried to buy up shares. Although this led to speculation that the pilots were going to make a bid for the airline, they ended up with just 2% of the company. But the ambitious move further isolated the pilots from the rest of the Aer Lingus staff.

Secure in the knowledge that the pilots' action will not be supported, and with the state out of the picture, the company used the new Belfast to Heathrow routes as a means of introducing lower wages and conditions for pilots.

And it might work. Up until this weekend, Impact had not even asked Siptu or cabin crew who are in the same union to support their planned action.

The company plans to hire fullycrewed planes to frustrate Impact's action. The pilots' union does not expect Siptu ground handling staff to black these planes. Even 20 years ago Aer Lingus would not have contemplated trying to break a strike in this way. And it would have been inconceivable that any union member would even contemplate co-operating with 'scab' labour.

The pilots have a case insofar as the company did ignore the union and existing agreements in setting inferior terms and conditions for Belfast. Aer Lingus points to a recent deal brokered by industrial relations troubleshooter Phil Flynn, which allows the company to apply local terms and conditions when setting up a base outside Ireland which has already been used by the airline.

But Flynn said last week that Belfast should not be considered 'outside Ireland', and if the move to Aldegrove had been on the agenda at the time he would have recommended the company negotiate terms and conditions for the new pilots with Ialpa. Though this may appear to swing the argument back in the pilots' favour, the company confidently maintains its hard-line approach.