Embodiments disclosed herein are directed to communicating time-critical ultra-low latency (ULL) data. An access point station (AP) communicates time-critical ULL data using aggregated MAC Protocol Data Unit (A-MPDU) preemption. When time-critical ULL data for a second associated STA (STA2) becomes available at a medium access control (MAC) layer of the AP during transmission of a physical layer protocol data unit (PPDU) to a first associate station (STA1), the AP may encode the time-critical ULL data in a new A-MPDU subframe for insertion before one of the A-MPDU subframes of the PPDU that has not yet been transmitted. The new A-MPDU subframe may be encoded to include zero-padding to set a size of the new A-MPDU subframe equal to a size of the A-MPDU subframe that has been preempted. The A-MPDU subframes 606 for STA1 may be encoded include a MAC address of the STA1 and the new A-MPDU subframe 608 may be encoded include a MAC address of the STA2.