Existing procedures have evolved to accommodate a wide range of non-normal operational situations.  Fortunately, most of these procedures translate readily into the AACV concept.  The most significant abnormal situations are discussed below.
2.3.1 Lost Communications: Aircraft Avionics Failure

As in other “lost com” situations in today’s system, a pilot who is unable to report an updated estimated time of arrival (ETA) is required to try to honor their last-reported ETA.  If they are running early, they reduce speed to adjust their arrival time.  If they are running late however, they may miss their window and have no way to make up sufficient time. The AACV system would have no way to know if they were truly just late or had gone “lost com” and are actually in the vicinity of the AACV, but not reporting.  Whenever failure of an aircraft to make a mandatory report or the loss of ADS-B data suggests that an aircraft has experienced avionics failure, the AACV system would respond by locking the ACV.  Of course, if ADS-B surveillance data for the lost-com aircraft later becomes available to the AACV system indicating the aircraft has not yet arrived in the airport vicinity, some operations could be resumed, if it is clear they can be completed before the lost-com aircraft arrives.
Federal regulations preclude extended IFR operations without ATC communication capability.10  If VMC exists, pilots are expected to land “as soon as practicable”. In the case of avionics failure enroute to or around an AACV airport in IMC, the following guidelines derived from the existing regulations could pertain:  If access to the ACV has been granted prior to avionics failure, the flight would immediately proceed to the appropriate IAF to initiate the approach and landing.  If access to the ACV was denied prior to avionics failure, the flight would remain outside the ACV until the EFC time received with the denial message, and then proceed to the appropriate IAF to initiate the approach and landing.  In either case, the ACV would remain locked until the aircraft is confirmed by ATC to have landed, diverted to another airport or departed the area.  The AACV would then be manually reset for normal operations.
2.3.2 Lost Communications: AACV Failure

From an aircraft's perspective, if an approach clearance request is made but no response is received, there may be no immediate way to tell if there is a communication failure in the aircraft transceiver or a failure of the ground equipment.  Before following procedures for lost communications, it would be prudent for the pilot to try to determine if it is the airport reception or their transmission/reception that has failed.  A test message could be included in the message set for this purpose, or facilities at another nearby airport may be of use.  If the pilot can confirm that the airport facility has lost capability, an approach under IFR using these procedures should not be initiated.  If an approach clearance has already been granted when airport automated sequence communication is lost, a pilot should be able to complete their approach assuming they still have appropriate approach guidance signal.
　
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