On 19th December 1998, the Thalys network was expanded to include a winter service to ski resorts in the French Alps. Branded as "Thalys Neige" ("Neige" being the French word for "Snow"), a direct service ran from Amsterdam Centraal to Bourg St. Maurice via Brussels, a total journey time of 8 hours 50 minutes.
In May 1999, the SNCF/SNCB cooperative "Westrail International" was renamed "Thalys International". This was followed by further expansion to incorporate a Thalys TGV service between Brussels, Charles de Gaulle Airport, and Marne-la-Vallée Chessy, this commencing on 28th November 1999. Marne-la-Vallée Chessy is the station located within the 5,000 acre Disneyland Paris complex, about 30-KM to the east of the capital, which opened on 19th May 1992 on an extension of the Paris RER (Réseau Express Régional) "A" line. On 29th May 1994, it became a combined RER/TGV station, when a 69-KM (43-mile) spur was commissioned to link LGV Nord with LGV Paris-Sud Est. In addition to Disneyland, the link served Charles de Gaulle Airport, the line passing through a tunnel underneath the runways and terminal buildings.
In parity with the aforementioned winter ski service, Thalys introduced a "Soleil" ("Sun") service to Valence, in south eastern France, in May 2000. From Brussels Midi, this was an 831.3-KM journey completed in 3 hours 26 minutes; on Saturdays only, the service ran from Amsterdam. In the same month, a daily service between Brussels and Geneva also began.
LGV Paris-Sud Est, linking the French capital and Lyon, had opened in its entirety as France's first dedicated high speed route in September 1983. In November 1989, works commenced to extend from Montanay (just north of Lyon, where the LGV route ended and met standard SNCF lines) to Valence. This extension was named "LGV Rhône-Alpes" and opened between Montanay and Saint-Quentin-Fallavier in December 1992, and from the latter to Valence in July 1994. Further southward extensions took place as part of the "LGV Méditerranée" project, which opened from Valence to Marseille on 10th June 2001, and included a branch to Nimes. In the following year, Thalys started a summer-only service to Avignon and Marseille.
On 15th December 2003, the first Thalys TGV train direct from Paris Gare du Nord arrived at Brussels Airport. This had departed the French capital at 06:25 and arrived at the airport at 08:35. Thalys had teamed up with SN Brussels Airlines to run one train in either direction on the route each weekday; the return working left Brussels Airport at 09.25 and arrived in Paris at 11:35. A single return working also operated on Saturdays and Sundays, to different timings, and these trains replaced the existing daily flights operated by SN Brussels Airlines between Brussels and Charles de Gaulle Airports. The logic was for Brussels to become a hub airport for those overseas passengers bound for Paris. Rather than passengers having to make the 23-KM trip from Charles de Gaulle Airport to the centre of the French capital, they could instead take a single TGV from Brussels to Paris Gare du Nord.
In 2007, German rail company DB bought a stake in Thalys, which resulted in a shareholding split as per the following: SNCF - 62%; SNCB - 28%; DB - 10%. DB's interest in Thalys ended in June 2013, when it was announced that the former was instead going to concentrate on its own range of "ICE" high speed services between Frankfurt and Brussels. In the meantime, Thayls had expanded the range of German services which, from 29th August 2011, included trains to Düsseldorf, Duisburd, and Essen. These had been helped along by the commissioning of the Belgian High Speed Line 3 on 12th June 2009, which linked Liege in Belgium with Aachen in Germany, a distance of 52-KM (32-miles). Beyond this, the only other part of the German railway network which permitted 300 KM/H (186 MPH) running was the high speed line between Cologne and Frankfurt, which opened to public traffic in May 2003.
High speed line progress had been made on Dutch territory, too. The "HSL-Zuid" (High Speed Line-South) from Amsterdam Schiphol Airport to Antwerp, the latter just over the border into Belgium, opened to international public traffic on 13th December 2009. This was after a difficult phase of making trains compatible with the line's signalling system. The line's commissioning reduced the Paris to Amsterdam Centraal journey time from 4-hours 9-minutes to 3-hours 17-minutes. Additionally, it gave rise to a new Thalys service from Amsterdam Centraal to Lille Europe: this commenced on 12th April 2014, with a journey time of 2 hours 40 minutes.
Although SNCF and SNCB had created the "Westrail International" brand in 1995 through which to run Thalys services, it was never a standalone operation. All decision making, accounting, and budgets came via the parent organisations. This changed when, on 31st March 2015, Thalys became an independent company, with headquarters in Brussels and an additional office in Paris. SNCF and SNCB retained a 60% and 40% split of the shares respectively.