If you make any changes in crew assigment on the flight, the 'Crew aware of trip' status in 'Legs Info' will get turned from 'ACK“ to '?' (see below).
1. Crew ECH & HOT assigned to the flight - the 'Crew aware of trip' status set to 'ACK'
2. Crew ECH is replaced with TAR - the 'Crew aware of trip' status is changed from 'ACK' to '?'