I've been googling and googling and the earliest passenger buildings seem to be called terminals.

first link about Croydon

...The airport owed its existence to two adjacent First World War airfields. The first, opened in December 1915, was Beddington Aerodrome, one of a ring of small airfields dotted around London to protect the capital against Zeppelin raids. It later became a training base. The second was Waddon Aerodrome, a test flying-ground attached to National Aircraft Factory no 1, which began operations in January 1918.

At the end of the war, the decision was taken to combine the two airfields, and to make them the 'Air Port of London' - the capital's official customs airport, the point of entry or departure for all international flights. Croydon Airport (or Croydon Aerodrome, as it was at first called) opened on 29 March 1920. The airport's origins as two separate airfields meant that it was physically divided by Plough Lane: the two halves were linked by a level crossing, where road traffic had to be halted at first by a man with a red flag, and later by a gate.

Regular scheduled flights were introduced, carrying passengers, mail and freight to Paris, Amsterdam and Rotterdam, and from 1923 to Berlin. A number of British air companies operated from Croydon (including Instone, Aircraft Transport and Travel Ltd, and Handley Page): most of these merged in 1924 to become Imperial Airways Ltd.

In the mid-1920s, the airport was remodelled. The airfield was extended, Plough Lane was closed permanently, and a new complex of buildings was constructed on the eastern side of the site, adjoining the Purley Way. These included a new terminal building - the first purpose-designed terminal in the world, opened on 2 May 1928 - the Aerodrome Hotel, and hangars.



this is about Gander in Newfoundland

Large huts which formerly housed USAAF personnel are now used to accommodate air travelers who are forced to stopover due to weather conditions or aircraft trouble. These accommodations, reconverted recently by the Newfoundland government into pleasant private quarters, proved a boon to commercial airlines in July, when over 300 passengers were stranded after Washington had grounded Constellation airliners.

The airlines “Mess” can accommodate 250 persons at each sitting and is operated on a 24 hour round-the-clock schedule, qualified French chefs, 46 Newfoundland-born waitresses, 50 waiters and kitchen assistants (10 percent of them being ex-servicemen) form the personnel of the catering staff who serve meals to the passengers of about 16 transatlantic airlines daily.

If future air traffic through Gander warrants it, the airlines operating the transatlantic flights are contemplating the erection of a modern hotel with every convenience. They are also blueprinting plans for an up-to-date streamlined air terminus building.23 Jul 1986 ... They are also blueprinting plans for an up-to-date streamlined air terminus building. ...
www.gaflight.org/development of commercial aviation.htm - Cached




Opened in 1938, it had the biggest landing field ever constructed. Business boomed following the onset of mass commercial flight after World War II, and major renovations were undertaken in the late 50's to accommodate the stream of passengers. Seeking to project a modern, stylish image of Canada, the government commissioned a futuristic terminal filled with avant-garde art and furniture.20 Mar 2005 ... Gander International Airport in Newfoundland was an unlikely hub in the ... of a new terminal at Gander International Airport in 1959. ...
travel.nytimes.com/2005/03/20/travel/.../20TGANDER.html - Similar





Many of the most famous airports that we know today were
conceived in the late 50’s and early 60’s
• Washington Dulles International (1958-1962)
• Newark International (1967-1973)
• San Francisco International (1967)
• Chicago Ohare International (1959-1963)
• Los Angeles International (1957-1961)
• Paris Orly-Ouest (1966-1971)
• Houston Intercontinental (1964-1967)
• Kansas City (1965-1972)
• Dallas/Fort-Worth Regional (1965-1973)

The early beginnings of American Airlines also started at Lunken in 1929 with passenger flights to Chicago. Lunken soon became the center of aviation in Cincinnati with increasing airline traffic and the periodic appearance of famous celebrities. 1929 saw 29,059 flights and 8,528-recorded passengers making their way through Lunken Airport.

In 1936 construction began on the distinctive terminal building still in use today.

The airfield was now operated by the City of Cincinnati, and long-term ... In 1936 construction began on the distinctive terminal building still in use today. But in early 1937 the greatest flood in recorded history spilled over the ...
www.cincinnati-transit.net/lunken.html - Cached - Similar


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Note added at 2 hrs (2011-01-13 21:54:07 GMT)
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the first link about Gander makes it fairly clear that passengers basically used huts. The 2nd link is about the new terminal.

20 Mar 2005 ... Gander International Airport in Newfoundland was an unlikely hub in the ... of a new terminal at Gander International Airport in 1959. ...
travel.nytimes.com/2005/03/20/travel/.../20TGANDER.html - Similar


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Note added at 2 hrs (2011-01-13 21:58:40 GMT)
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which won't paste properly!

Foynes was another early seaplane airport; again called "terminal"

During the late 1930s and early 1940s, land-based planes lacked sufficient flying range for Atlantic crossings. Foyne was the last port of call on its eastern shore for seaplanes. As a result, Foynes would became one of the biggest civilian airports in Europe during World War II. Surveying flights for flying boat operations were made by Charles Lindbergh in 1933 and a terminal was begun in 1935.[2] The first transatlantic proving flights were operated on July 5, 1937 with a Pan Am Sikorsky S-42 service from Botwood, Newfoundland and Labrador on the Bay of Exploits and a BOAC Short Empire service from Foynes with successful transits of twelve and fifteen-and-a-quarter hours respectively. Services to New York, Southampton, Montreal, Poole and Lisbon followed, the first non-stop New York service operating on June 22, 1942 in 25 hours 40 minutes.

[edit] Foynes Flying Boat MuseumAll of this changed following the construction and opening in 1942 of Shannon Airport on flat bogland on the northern bank of the Estuary. Foynes flying-boat station closed in 1946. A college for the learning of the Irish language was opened in the former terminal in 1954.
Foynes flying-boat station closed in 1946. A college for the learning of the ... The Foynes Flying Boat Museum contains much memorabilia from that era, ...
en.wikipedia.org/wiki/Foynes - Cached - Similar




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Note added at 2 hrs (2011-01-13 22:00:56 GMT)
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en.wikipedia.org/wiki/Foynes - Cached - Similar


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Note added at 24 days (2011-02-07 00:40:57 GMT) Post-grading
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thanks, yes, could find no use of "station" for buildings as e.g. above, "Foynes station" whole area and building ="terminal"

Glad to help:-)