I looked through the FT forum for a dedicated thread and this one seems to be most relevant.

FRA terminal 3 opening is planned for 2026 (probably end of year, but not specified anywhere). Do you have any further update / insights on the FRA extension?
Source 1: https://www.fraport.com/en/business-...erminal-3.html
Source 2: https://terminal3.frankfurt-airport.com/en/

In your view, if already FRA is very packed and changing terminals (especially A-B) is painful to go through the underground tunnel, how do you see the potential transfer T1 -> T3? Apparently just 9 minutes by Sky Line, but knowing FRA, 1h transfer between T1-T3 seems veeery tight. Any thoughts, insights from your side? Do you think this T3 would realistically make T1 and T2 less crowded?