Ryanair's USD$1.9 billion bid for Aer Lingus, which would pair a low-cost carrier with a traditional airline, could represent the model for consolidation in the industry, experts say.

"This is the first step in what I think will be the next generation of airline consolidation," said Stuart Klaskin, a partner of KKC Aviation Consulting.

Merger speculation, especially in the United States, has been rampant recently as the financial performance of airlines improves. And with over 260 carriers in the world, the industry is seen as unwieldy and ripe for thinning.

Although the Aer Lingus board has rejected the bid made on Thursday as undervalued, Ryanair's plan would link a rapidly growing point-to-point carrier with a long-haul national carrier.

Traditional carriers have for years been losing domestic or short-haul market share to low-cost carriers and the trend is expected to continue. This has led many legacy carriers, such as United Airlines and American Airlines to expand international routes, which are less contested, but often more complex to operate.

Combining a low-cost airline with a legacy carrier addresses the weaknesses of the two business models. Legacy carriers struggle to compete domestically because of higher costs, but low-cost airlines struggle with long-haul service, said Klaskin.

Airline consultant Robert Mann said these combinations could take the form of full-blown mergers, but more modest partnerships, such as Southwest Airlines' alliance with ATA Airlines, would be easier to carry out.

But there will be cultural clashes.

Although both are based in Ireland, Aer Lingus and Ryanair would be uncomfortable bedfellows, said Randy Babbitt, chief executive of aviation advisory firm Eclat Consulting.

"It would be a very difficult cultural merger," he said.

Ryanair is an aggressive, no-frills carrier, while Aer Lingus is a legacy national carrier that has strong links to the Irish government, its largest shareholder.

Evidence that there will be problems surfaced on Friday, when Irish opposition politicians and union officials decried the merger proposal.

Some industry experts also have doubts about the rationale of merging low-cost and legacy carriers.

"I don't really see that model would work," said Geert Boven, acting chief executive of Abu Dhabi-based Etihad Airways. "It's two completely different business models."