Although this thread is for passengers connecting within FRA T1, there are occasional questions about connecting to/from T2. This announcement about the restriction to the Skyline shuttle service might be useful for some.
The Sky Line shuttle service will not be operating between Terminals 1 and 2 from July 11 thru August 5, 2016, due to construction work. During this period, the Sky Line will only operate between the stations of Terminal 1 (Concourses B and A/Z). To ensure passenger transportation between Terminals 1 and 2, replacement buses will be in service operating on a frequent schedule (see map [below]). Please allow some extra time for transferring between the terminals. Appropriate signs have been provided and extra staff will be available to assist customers. Only during the weekends on July 16-17 and July 23-24, the Sky Line will operate as usual.