Almost three years on from announcing the acquisition of ITA Software and 18 months after launching a domestic-only service, Google Flight Search is finally heading overseas.

From today, travellers in the UK, France, Italy, Spain and the Netherlands will now be able to look for flights on Google Flight Search in the same way as their North American counterparts.

Flights originating in those countries to any other airport in the world will be included in the system - a massive leap in functionality from the slightly limited array of services available until now.

Some low cost carriers are missing, inevitably, such as European giants easyJet and Ryanair - the former being easier to pick up as a metasearch engine these days, but Ryanair almost non-existent on comparison sites.

Prices will be displayed in the relevant local currency and searches will be available at a country level (London to Greece, for example) as well as specific airports.

Searches can be carried out in eight languages (English, French, Italian, Spanish, Basque, Catalan, Galician and Dutch) and all existing search tools, such as lowest fare graphs, maps and "relevant flights", are also included in the roll-out.

ITA Software, seen as a North America-focused provider until now, is powering this initial phase of the roll-out (rather than another technology firm working with Google behind the scenes).

Google says it is hoping to bring the service to more countries in due course, as it expands its relationship with other airlines.

In the some respects the launch of Google Flight Search into Europe is a bit of a non-story, flight search providers expand their services to new territories all the time.

But the background is often more interesting than the announcement.

Within a few months of Flight Search being launched in the U.S., Google said the international roll-out would be "coming soon" - two words which have since gone on to haunt the company given that such expansion didn't materialise for another 18 months.

In November last year, vice president of travel at Google (and ex-CEO of ITA Software), Jeremy Wertheimer, said the company was taking a more cautious approach to taking Google Flight Search outside of North America.

"International expansion requires working with partners," Wertheimer said, "and to do that requires time in the airline space." Furthermore, growing internationally was "a long game" and Google was spending a lot of effort "scientifically looking at things".

Of course, since November last year the world of international travel metasearch (on the flight side) has shifted considerably.

On the eve of Wertheimer claiming Google had a new and cautious nature to launching in new markets, Priceline went and bought U.S. metasearch giant Kayak for 1.8 billion pounds.

Meanwhile, Skyscanner continues its rapid growth around Europe and elsewhere.

So, while Google will never admit it, the need to push Flight Search in to new markets is now more important than ever.