Not my patch - I'm based in Wiltshire - but this is worth engaging with properly rather than letting it dissolve into the usual ". It was swamp gas". Dismissal.
Highway 89 cuts through some genuinely interesting terrain near Flagstaff, and that corridor towards the Navajo Nation has a surprisingly dense history of aerial anomaly reports going back decades. Worth cross-referencing with NUFORC submissions for that date range before anything else.
A few things I'd want to know before forming any view:
Formation or singular source? Multiple lights behaving coherently versus independently changes the analysis considerably, Duration and angular movement - did anyone capture even basic smartphone footage?, Any corroborating radar data? Flightradar24 occasionally throws up interesting gaps
I run a FLIR thermal setup for my own fieldwork here on Salisbury Plain, and the number of incidents that look dramatic on standard video but resolve into something mundane under thermal imaging is frankly embarrassing. Equally, the reverse is sometimes true.
That said, I'm not going to reflexively dismiss this. The Southwest US corridor produces a disproportionate number of reports that resist easy explanation, and Tuesday night conditions matter enormously - cloud base, military exercise NOTAMs, visibility.
Anyone actually there with direct observation accounts, please post specifics rather than impressions. Vague ". It was amazing". Contributions aren't useful. Times, bearings, duration, and any physiological effects noted during or after observation.