Traditionally, budget airline Ryanair has operated out of secondary airports, a business model that has proved to be successful — so far.
But faced by declining growth opportunities, the Irish carrier is now adopting a change of tack by moving into main airports in order to tap lucrative corporate travel.
It also wants to see off competition from IAG-owned Vueling, which is chasing the same passenger profile.
To that end, Ryanair has announced ten new routes from the Brussels' main Zaventem airport. These will launch in February and will be operated by a dedicated fleet of four planes that are in addition to its existing flights from the less convenient Charleroi airport.
Destinations to be served from Zaventem include Barcelona (El Prat), Lisbon, Rome (Fiumicino), Valencia and Venice.
Expansion is greater still at Rome, where Ryanair will base six aircraft at the city's main Fiumicino airport by next April, rising to 12 aircraft by the autumn.
Not all new routes from Fiumicino have been announced, but they will include flights to Brussels (Zaventem) and Barcelona (El Prat) in addition to three Italian destinations — Catania, Palermo in Sicily, and Lamezia in the south.
Ryanair will continue to operate from Ciampino which, ironically, is closer to Rome city centre than is the city's main Fiumicino airport.
Recently, IAG-owned Vueling also announced a huge expansion at both the above-mentioned airports, also targetting the business traveller. It is adding seven new routes from Brussels plus 24 new routes from Rome.
Aviation expert John Strickland, of JLS Consulting, said: "When Ryanair sees a significant strategic threat it responds hard. That was the case when Go competed [against Ryanair] between Scotland and Dublin or Easyjet [against Ryanair] between Gatwick and Ireland."
Passengers can only win in the latest round of air wars. The losers will be the home airlines, namely Brussels Airlines and Alitalia.
Of course, the latter deliver all the trappings of traditional airlines like better onboard service, lounges, loyalty schemes, business classes etc. But the cost bases of Brussels Airlines and Alitalia are much higher than those of the low-cost carriers.
It means they cannot compete on price and for a good many people it is the price of the ticket which is all-important.
What about Vueling? Well, I have followed the fortunes of low-cost carriers ever since the days of Laker Skytrain in the late '70s. History shows that only those carriers with the lowest operating costs win in the end.