Well that's a bit clearer...
Positive acknowledgement from the aircraft consists of the transmission of the Uplink Block Identifier of the correctly received block. Positive acknowledgement from the ground station consists of a similar transmission of the Downlink Block Identifier.
Acknowledgements are placed in the Technical Acknowledgement field.
So, there is automated ackowledgement from the aircraft from uplink block transmission.
To resolve the suggested *anomaly* we now need to determine whether the last uplink to Flight 175 was acknowledged by the aircraft or not.
Logic would suggest not, as it's in bits in and around WTC 2 at that time.
So another question that must be attempted to answer is whether the messages on the scanned printouts were acknowledged or not.
Doesn't seem like the *Technical Acknowledgement* field is included within the printout, so not quite sure how to progress.
Hmm.
