Cockpit representatives are urging caution from crews when receiving controller-pilot datalink clearances, particularly altitude changes, after incidents in which delayed messages were transmitted to the wrong flight.
The issue emerged with the Iridium satellite communications network in October when queued clearances were subsequently delivered to aircraft systems hours later, when they no longer applied.
While the Iridium issue has been corrected, international pilots' federation IFALPA says crews should "exercise caution" when cleared for flight-level changes via CPDLC, particularly if the clearance is "not in response" to a request.
The federation says crews have no access to information indicating the time at which an uplinked CPDLC message was transmitted.
It adds that the possibility of an old clearance being delivered past its validity time, or to the wrong aircraft, "cannot be ruled out".
Crew should clarify any unexpected altitude change clearance, it states, while mitigation measures are being developed to eliminate the risk.