I knew about the iconic weapon on top of the pyramid from my first playthrough, so I was like "I'll grab that then I'll head over, there's probably no time limit"
Got to the top of the pyramid and Songbird was like "V, WHERE ARE YOU, GET TO THE PLANE!"
Got to the bottom and as I was running over Songbird started talking again, "That's it, the presidents dead, you failed V, prey that we never meet"
SB dips and you wake up in a random spot and that's it, mission failed; then you get a call from Mr Hands to give you missions :>
Anyway, just gonna load up from an earlier save; but that's funny you can just straight up fail the main storyline from the DLC