BBC News Online looks at what the deal will mean for the airline industry and travellers.

Why is Ryanair buying Buzz?

Ryanair chief executive Michael O'Leary has previously poured scorn on the idea of growing the company by acquisition. He prefers organic growth.

But he has said the Buzz offer is "one we could not refuse".

Ryanair will pay �15.1m for its struggling rival, but Buzz is thought to have around �11m in the bank, making the true price about �4m.

What does Ryanair get for its money?

It immediately gains another 21 routes from its main UK hub, London Stansted, to Germany, Holland, France and Spain and two French domestic routes.

It will also take over six Boeing 737-300s and eight BAE 146 aircraft, although the BAE planes will be returned to KLM by March 2004.

What's in it for KLM?

The Dutch flag-carrier gains much-needed cash to pay for a settlement with Italy's Alitalia, following their aborted merger.

It will also boost KLM's struggling profits.

What impact will the deal have on air fares?

It should intensify competition between Ryanair and EasyJet in key markets, which is potentially good news for consumers.

The two companies now dominate Europe's budget air market, following EasyJet's purchase last year of Go!.

So there is likely to be no let-up in price-cutting tactics from either firm.

So which budget airline is the biggest?

Both EasyJet and Ryanair now claim to be Europe's biggest low-cost carrier.

They both have a similar number of routes, but EasyJet currently carries more passengers, around 20 million.

Ryanair, however, is worth three times more than EasyJet on the stock market.

Will there be more acquisitions?

Ryanair has said its ambition is to be Europe's biggest airline.

But although it is growing at a dizzying rate - and is on course to double its passenger numbers in five years - it is unlikely to be able to achieve this goal without further acquisitions.

Michael O'Leary has reportedly expressed an interest in acquiring Ireland's struggling flag-carrier Aer Lingus, even though such a move would expose Ryanair to the volatile transatlantic market.

Mr O'Leary has acknowledged the dangers of rapid expansion, but in the current climate Ryanair can afford to capitalise on the troubles of its larger, full service rivals.

What can Ryanair do to make Buzz profitable?

It will axe Buzz's unprofitable routes and pile more planes on to moneymaking routes.

Both airlines principally operate out of Stansted, so economies of scale should not be hard to achieve.

Analysts expect Ryanair to return landing slots at overcrowded airports such as Paris Charles De Gaulle and Amsterdam to KLM.

These do not fit in with Ryanair's business model of quick turnarounds at cheaper secondary airports.

Ryanair expects Buzz to return to profitability within a year.