Major disruption around Frankfurt (Main) from July 16th

The railway which links Mannheim Hbf, which is a hub station on the German rail network, to both Frankfurt (Main) Hbf and the high-speed rail station at Frankfurt Airport, is typically used by up to 3 x ICE trains per hour each way.
It's also used by most of the trains which connect Frankfurt (Main) with France.

The high-speed rail station at Frankfurt Airport, the Frankfurt Flughagen Fernbahnhof, is at the southern end of the high speed line which links Frankfurt (Main) with Köln / Cologne - and the city centre to city centre ICE trains which use this line, also use the northern end of the line which links Mannheim to Frankfurt (Main).

However from July 16th, until the pan-European timetable refresh on December 15th, the route to /from Manheim is closed for maintenance works.
Plus from July 16th to July 29th inclusive, the line is also closed between Frankfurt Flughagen Fernbahnhof and Frankfurt (Main) Hbf, the main city centre station - though the local and regional trains, which use a separate station at the airport, will be unaffected.

As a consequence of this maintenance work:
2. From July 16th until December 14th inclusive, the ICE services which typically connect Frankfurt Flughagen Fernbahnhof and Mannheim, will be diverted on to longer slower routes - and most of them won't be calling at the airport station.
3. From July 16th until December 14th inclusive, the ICE services which typically connect Frankfurt (Main) Hbf and Mannheim will be diverted on to a different route between the two cities - and will also have the start and finish points of their usual routes significantly altered.
4. The Frankfurt ↔ Paris trains which typically travel via Strasbourg won't be available between Frankfurt (Main) and Mannheim from July 16th until December 14th; the Frankfurt ↔ Paris trains which travel via Saarbrucken are not impacted.
5. The daily Frankfurt ↔ Marseille train will also be turning around in Mannheim during these dates.
6. The daily EC trains which typically take a Hamburg - Bremen - Dortmund - Cologne - Bonn - Koblenz ↔ Mainz - Karlsruhe - Baden Baden - Basel - Interlaken or Zurich route, have been withdrawn until at least December 14th.
7. The IC / ICE trains which typically take a Hamburg - Bremen - Dortmund - Cologne - Bonn - Koblenz ↔ Mainz - Mannheim - Heidelberg - Stuttgart route, won't be operating south of Koblenz until December 14th.

The works will impact the usual pattern of rail services at locations beyond Frankfurt (Main) and Mannheim, with alterations to the usual timetable at stations across Germany - and during this time the ICE trains which travel between Germany and Switzerland will also be affected.

The only ICE service which typically calls in both Frankfurt Flughagen Fernbahnhof and Frankfurt (Main) hbf, which won't be significantly impacted at all from July 16th, is the Wiesbaden - Mainz - Frankfurt Flughagen Fernbahnhof - Frankfurt (Main) - Erfurt - Leipzig - Dresden route; While Frankfurt Flughagen Fernbahnhof is closed it will instead use the regional rail station at Frankfurt Airport.

In order to minimise disruption to the overall German rail timetable, the entire routes of the ICE services which typically travel between Mannheim and either Frankfurt Flughagen Fernbahnhof of Frankfurt (Main) Hbf, are being altered until December 14th inclusive.
As a consequence Frankfurt (Main) will retain the same volume of direct trains to and from Basel, Berlin, Hamburg, Hannover and Stuttgart, but the impact will actually be greater at those more distant cities.

The key changes are summarised below (not all station calls have been included).
All services operate every two hours

München ↔ Hamburg via Stuttgart and Köln Hbf

Usual route:
München - Augsburg - Ulm - Stuttgart - Mannheim ↔ Frankfurt Flughafen Fernbf - Siegburg/Bonn - Köln Hbf - Dortmund - Bremen - Hamburg

to December 14th:
Stuttgart - Heidelberg - Darmstadt ↔ Frankfurt Flughafen Fernbf - Siegburg/Bonn - Köln Hbf - Dortmund - Bremen - Hamburg
Heidelberg isn't usually connected to Frankfurt Airport / Flughafen by ICE trains.

(München) - Stuttgart ↔ Dortmund - (Hamburg) via Köln Messe / Deutz

Usual route:
(München - Augsburg - Ulm) - Stuttgart - Mannheim ↔ Frankfurt Flughafen Fernbf - Siegburg/Bonn - Köln Messe / Deutz - Dortmund - (Bremen - Hamburg)

July 16th to December 14th:
München - Augsburg - Ulm - Stuttgart - Mannheim ↔ Mainz - Wiesbaden - Köln Messe / Deutz - Dusseldorf

München - Stuttgart ↔ Leipzig - Berlin

Usual route:
München - Augsburg - Ulm - Stuttgart - Mannheim ↔ Frankfurt(Main) Hbf - Fulda - Erfurt - Leipzig - Halle(Saale) - Berlin

to December 14th:
München - Augsburg - Ulm - Stuttgart - Mannheim ↔ Mainz - Frankfurt(Main) Hbf - Fulda - Kassel - Hannover - Hamburg
As a consequence Ulm and Stuttgart will temporarily be deprived of direct rail links with Leipzig and Halle (Saale).

Stuttgart - Mannheim - Frankfurt Flughafen ↔ Hannover - Hamburg

Usual route:
Stuttgart - Mannheim - Frankfurt Flughafen ↔ Frankfurt(Main) Hbf - Fulda - Kassel - Hannover - Hamburg

to December 14th:
Stuttgart - Darmstadt ↔ Frankfurt(Main) Hbf - Fulda - Kassel - Braunschweig - Wolfsburg - Berlin
As a consequence Frankfurt Flughafen / Airport will temporarily be deprived of direct rail links with Hannover.
Also the only trains which will travel between the airport and Hamburg during these dates will be taking the longer route via Köln.

(Interlaken) - Basel ↔ Braunschweig - Berlin

Usual route:
(Interlaken - Bern) - Basel - Freiburg(Breisgau) - Offenburg - Karlsruhe - Mannheim Hbf ↔ Frankfurt(Main) Hbf - Fulda - Erfurt - Kassel - Braunschweig - Wolfsburg - Berlin

to December 14th:
(Interlaken - Bern) - Basel - Freiburg(Breisgau) - Offenburg - Karlsruhe - Mannheim Hbf ↔ Mainz - Frankfurt(Main) Hbf - Fulda - Erfurt - Kassel - Hannover - Hamburg

Zurich - Basel ↔ Hannover - Hamburg

Usual route:
(Chur) - Zurich - Basel - Freiburg(Breisgau) - Baden-Baden - Karlsruhe - Mannheim Hbf ↔ Frankfurt(Main) Hbf - Fulda - Erfurt - Kassel - - Hannover - Hamburg

December 14th
Zurich - Basel - Freiburg(Breisgau) - Baden-Baden - Karlsruhe - Darmstadt Hbf ↔ Frankfurt(Main) Hbf - Frankfurt(Main) Hbf - Fulda - Erfurt - Leipzig - Halle(Saale) - Berlin
When this service was altered to this route during 2023, the trains were ultimately turned around in Basel.
If this does NOT happen, then a short term gain will be direct rail links between Switzerland's largest city and both Leipzig and Berlin, but Zurich will temporarily be deprived of a direct daytime rail link to/from Hannover and Hamburg.

Basel ↔ Köln - Hamburg

Usual route:
Basel - Freiburg(Breisgau) - Offenburg - Karlsruhe - Mannheim Hbf ↔ Frankfurt Flughafen Fernbf - Siegburg/Bonn - Köln Hbf - Dortmund - Bremen - Hamburg

to December 14th: (see the note below)
Basel - Freiburg(Breisgau) - Offenburg - Karlsruhe - Mannheim Hbf ↔ Weisbaden - Köln Hbf
As a consequence Frankfurt Flughafen / Airport will temporarily be deprived of direct rail links with Basel, Freiburg(Breisgau), Karlsruhe and Offenburg.
Also because this service will be turning around in Köln there will be fewer trains travelling between Frankfurt Airport and both Bremen and Hamburg.

Basel ↔ Köln - Amsterdam

The daily ICE train which took a Basel - Freiburg(Breisgau) - Offenburg - Karlsruhe - Mannheim Hbf ↔ Frankfurt Flughafen Fernbf - Siegburg/Bonn - Köln Hbf - Arnhem - Utrecht - Amsterdam route has been permanently withdrawn.
It can't resume from the December 15th timetable change due to scheduled works on the line between Duisburg and Arnhem.

Also worth knowing:

From September 2nd the Frankfurt ↔ Milan ECE train is scheduled to return, and in both directions it will be taking a new route of Milano Centrale - Como - Lugano - Bellinzona - Zurich - Basel ↔ Freiburg(Breisgau) - Offenburg - Karlsruhe - Mannheim - Frankfurt (Main).

Because many ICE services are having to be routed via Mainz

• the IC trains which typically operate at least every other hour on a Stuttgart - Heidelberg - Mannheim - Mainz - Koblenz - Bonn ↔ Cologne - Dortmund - Bremen - Hamburg route won't be operating south of Koblenz until December 14th.
• The daily EC trains which typically take a Hamburg - Bremen - Dortmund - Cologne - Bonn - Koblenz ↔ Mainz - Karlsruhe - Baden Baden - Basel - Interlaken or Zurich route, have been withdrawn until at least December 14th.