innerdeutsch
domestic German
Relating to or taking place within the borders of Germany.
Die Kosten für innerdeutsche Flüge sind in letzter Zeit gestiegen.
The costs of domestic German flights have risen recently.

domestic German / intra-German
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domestic German
Relating to or taking place within the borders of Germany.
Die Kosten für innerdeutsche Flüge sind in letzter Zeit gestiegen.
The costs of domestic German flights have risen recently.

The adjective consists of the prefix 'inner-' and the word 'deutsch' (German). The prefix 'inner-' means 'inside of' and helps you understand the meaning 'within Germany'.
Die innerdeutschen Grenzen wurden 1990 geöffnet.
The intra-German borders were opened in 1990.
'Innerdeutsch' (domestic German / intra-German) is almost always used as an attributive adjective directly before a noun. Predicative use, e.g. 'Der Handel ist innerdeutsch' (The trade is intra-German), is very rare.
Der innerdeutsche Flugverkehr hat stark zugenommen.
Domestic German air traffic has increased sharply.
In its modern meaning, 'innerdeutsch' (domestic German) is often combined with topics such as transport, trade, or travel. Typical collocations are 'innerdeutsche Flüge' (domestic German flights), 'der innerdeutsche Handel' (domestic German trade), or 'der innerdeutsche Reiseverkehr' (domestic German travel).
Für innerdeutsche Bahnreisen gibt es oft Sparangebote.
There are often saver offers for domestic German train journeys.
You can recognize the historical meaning from the context. If it is about the period before 1990, the GDR and the FRG, or the division of Germany, it refers to the relationship between the two German states.
Die innerdeutschen Beziehungen waren ein zentrales Thema des Kalten Krieges.
Intra-German relations were a central topic of the Cold War.
international
'international' and 'innerdeutsch' both describe the area in which something takes place. 'international' means that several countries are involved or that a border is crossed. 'innerdeutsch' means that something happens within Germany. In historical texts, 'innerdeutsch' can also refer to relations between West Germany and East Germany before 1990. The confusion arises because both words often appear in connection with politics, transport, or trade. If Germany is only the internal framework, 'innerdeutsch' fits; if other countries are involved, 'international' fits.

Wegen des Streiks werden morgen viele innerdeutsche Flüge ausfallen.
Because of the strike, many domestic German flights will be canceled tomorrow.
Unser Unternehmen sucht internationale Partner in Frankreich und Spanien.
Our company is looking for international partners in France and Spain.