Read the segment table, not the company total. Northrop Grumman's 2021 Form 10-K breaks backlog out by business, and the Aeronautics Systems line shows total backlog falling roughly 24% during 2021. A consolidated backlog figure can stay healthy while one segment's runway shortens — which is exactly the kind of divergence the segment disclosure exists to surface.
For a markets desk, a 24% segment-backlog decline is a forward-revenue flag worth understanding before it shows up in sales. Aeronautics backlog can fall for benign reasons — a large prior-year award being worked off, timing between program phases — or for structural ones — a program maturing without a replacement. The filing's job is to disclose the number; the analyst's job is to read which kind of decline it is.
The structural context is that Northrop runs distinct segments — Aeronautics, Defense, Mission and Space — each on its own program clock. Space backlog dynamics differ from Aeronautics dynamics; a strong space book can offset a softening aeronautics book at the company level. That is precisely why backlog should be read by segment.
The forward question entering 2022: whether new Aeronautics awards refill the runway or whether the decline persists into recognized sales. Track segment book-to-bill, not just the consolidated total. Filing on sec.gov; index via EdgarBeast.