The plan is to have four terminals at Heathrow by 2012
It might be expected that BAA's Heathrow Airport internet home page would trumpet the public opening of Terminal 5.
But, significantly, the biggest headline on heathrowairport.com is "Over 50 airlines at Heathrow are moving terminal - check where to go".
The British Airways move to T5 may have taken years of planning, but for the users of Heathrow, the upheaval has only just begun. The late bags, cancelled flights and unhappy passengers seen on the first day of T5 operations might be just a foretaste of future problems.
While it will take BA the best part of a year to move the vast majority of its operations from three terminals to T5, the knock-on for passengers flying with other airlines may last even longer.
And the reason for the likely delays: airline alliances.
Profit and loss
Since the late 1990s, major carriers have been allying themselves with their former rivals.
For some, this means they can offer their customers a bigger range of destinations and connections.
In other cases, airlines have effectively been able to sell seats on another carrier's aircraft, as if it was their own flight. This is known as code-sharing.
Allowing another airline to fly the route means companies can cut unprofitable services. They can also use their own planes to open up more lucrative destinations, or fly more often on popular routes.
The three main alliances, Oneworld, Star Alliance and Skyteam, have now begun to co-locate their member airlines at the world's key airports.
HEATHROW CHANGES 2008-2012
27 March 2008: BA starts move to T5
30 March 2008: Skyteam airlines Continental, Delta and Northwest join associates KLM and Kenya Airways in T4
30 April 2008: Most BA long-haul flights move from T4 to T5
10 June 2008: Star Alliance members Air New Zealand and United move from T3 to T1
17 Sept 2008: Remaining BA European flights move from T1 to T3
17 Sept 2008: Oneworld's European airlines switch from T1 and T2 to T3
Oct-Nov 2008: Star Alliance airlines at T2 - Lufthansa, Austrian, Swiss, TAP and Croatia - relocate to T1
Early 2009: BA long-haul services to Australasia move from T4 to T3
2012: Star Alliance long-haul airlines move out of T3 to Heathrow East
The change to "alliance" terminals is now gathering pace - and Heathrow has recognised that it has to follow suit or lose custom to other global hubs.
British Airways is a founder member of the Oneworld alliance - which includes airlines such as American, Finnair and Japan Airlines.
But T5, for all its scale and fanfare, will not be the alliance's Heathrow home - the 15 years from drawing board to opening means it is not big enough for all of BA's operations, let alone its allies.
Instead, BAA has said it will co-locate Oneworld members to Terminal 3, which is nearest to T5.
While T3 has been recently refurbished, it is still a building which can trace its origins to 1955.
However, BAA insist that the recent modernisation of T3, plus plans to spend another £1bn on facilities over the next decade, has brought about real improvements.
The youngest of Heathrow's first four terminals, Terminal 4, is going to be the home of the Skyteam Alliance - made up of airlines such as Air France, Delta, KLM, Alitalia, Continental and Korean Airlines.
Despite opening in 1986, Terminal 4 is no longer in the first flush of youth.
Its previous tenants, British Airways, endured problems with an unreliable baggage system breaking down. Also, T4's position on the edge of the airfield made transfers to the central area less than straightforward.
20 years old, Terminal 4 will be given a makeover
BAA has promised to improve the terminal, once BA has fully vacated in 2009.
When Skyteam's European member airlines leave Terminal 2 - Heathrow's oldest passenger building - it will be demolished.
BAA has ambitious plans - approved by the local council - to build an entirely new facility named Heathrow East.
It hopes this new building, claimed to be on the same scale as T5 and providing the same ambience, will be ready in time for the London Olympics in 2012.
It would be occupied by Virgin Atlantic and the Star Alliance - the largest of the airline groupings.
Star is the most widely-scattered of the alliances after Oneworld. Its members currently operate out of Terminals 1, 2 and 3.
Terminal 2 will be pulled down to make way for a new terminal
That makes the job of transferring passengers - hopefully with their bags - a major exercise.
Those airlines not currently in an alliance are expected to move to Terminal 4 during the course of 2008.
BAA and the airlines hope that by 2012 Heathrow will be transformed.
But it is the ultimate transformation - longer-term plans to build a third runway plus a Terminal 6 - that continues to overshadow Heathrow.
Added to that is the environmentalist argument: green groups say that the travelling public has to fall out of love with flying - or rein in their desire for cheap flights - if the battle against climate change is to be won.
Some might say that the disruption which is expected to affect Heathrow users for the next four years would not be necessary if more was done to dissuade us from flying.