Originally Posted by
mfirst
... and if there are fees, why should we be responsible when we didnt change the flights? ,,,
Separate tickets, the schedule risk falls 100% on you.
If you can not change the TK flight to an earlier flight or come in the night before, than you will need to change your UA/LH flights. You will need to see what the options are (just do a dummy booking to check) and call to change -- you will be subject to a change fee (varies based on ticket rules -- figure at least $300-$400 and fare change for the new ticket -- could be nothing, could be substantial.
Note if you change now before outbound, you will be potential hit with fare changes in the outbound leg also. If you wait until you have flown the outbound, then only the return refares but changing close in may have even higher fare change. A lot depends on the ticket rules and available fare class. Impossible to give a definitive answer in the abstract. A good agent could help provide information,